Infix/Postfix evaluator terminating issue - c++

I've got a few different functions that on their own work fine. Now I am trying to put them together into one file. My debugger is throwing segmentation faults in the infixToPostfix function.
When I watch the ns variable, it does not show anything getting assigned to it, but it prints out the postfix expression when I actually run the code. When ns passes into PostfixEvaulation, it runs to the top member function of TemplateStack and crashes with:
terminate called after throwing an instance of "std::string"
This only happens when I pass a string with an operator. When I pass a string of just numbers, everything runs fine,
but it still does not seem to call PostfixEvaluation.
#include <iostream>
#include <sstream>
#include <string>
#include <typeinfo>
using namespace std;
//Class Template Stack declaration
template <class T>
class TemplateStack {
public:
typedef T type;
TemplateStack()
{
max_size_ = 50;
TopOfStack = 0;
data_ = new T[max_size_];
} //Default Constructor taking no parameters
void push(T element)
{
if (TopOfStack == max_size_)
throw string("Stack's underlying storage is overflow");
TopOfStack++;
data_[TopOfStack] = element;
}
void pop() {
if (TopOfStack == -1)
throw string("Stack is empty");
TopOfStack--;
}
T top() {
if (TopOfStack == -1)
throw string("Stack is empty");
return data_[TopOfStack];
}
private:
int TopOfStack; //Generic data type for the top element of stack
size_t max_size_;
T* data_;
};
//Function to Evauluate the Postfix notation expresion
int PostfixEvaulation(string input){
//string input;
int operand1, operand2, result,number;
TemplateStack<char>operation;
stringstream temp;
int i=0;
while (i < input.length())
{
if (isdigit(input[i]))
{
operation.push(input[i]);
}
else
{
operand2 = operation.top();
temp << operation.top();
operation.pop();
operand1 = operation.top();
temp << operation.top();
operation.pop();
switch(operand1,operand2)
{
case '+': result=operand1 + operand2;
break;
case '-': result=operand1 - operand2;
break;
case '*': result=operand1 * operand2;
break;
case '/': result=operand1 / operand2;
break;
}
operation.push(result);
}
i++;
}
cout << "The result is: "<<temp.str()<<endl;
//cin.ignore(numeric_limits<streamsize>::max(), '\n');
return 0;
}
//Function to return precedence of operators
int prec(char c)
{
if(c == '^')
return 3;
else if(c == '*' || c == '/')
return 2;
else if(c == '+' || c == '-')
return 1;
else
return -1;
}
//Function: Convert Infix to Postfix
void infixToPostfix(string s)
{
TemplateStack<char> st;
st.push('N');
int l = s.length();
string ns;
for (int i = 0; i < l; i++) {
// If the scanned character is an operand, add it to output string.
if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z')) {
ns += s[i];
}
// If the scanned character is an ‘(‘, push it to the stack.
else if (s[i] == '(') {
st.push('(');
}
// If the scanned character is an ‘)’, pop and to output string from the stack
// until an ‘(‘ is encountered.
else if (s[i] == ')') {
while (st.top() != 'N' && st.top() != '(') {
char c = st.top();
st.pop();
ns += c;
}
if (st.top() == '(') {
char c = st.top();
st.pop();
}
}
//If an operator is scanned
else {
while (st.top() != 'N' && prec(s[i]) <= prec(st.top())) {
char c = st.top();
st.pop();
ns += c;
}
st.push(s[i]);
}
}
//Pop all the remaining elements from the stack
while (st.top() != 'N') {
char c = st.top();
st.pop();
ns += c;
}
cout << "Here is the ns variable: "<< ns << endl;
PostfixEvaulation(ns);//Call the PostFixEvaluationFunction with the ns (postfix notation) variab
}
//Function: User inputs Expression
void GetInput(){
string input;
cout << "Enter Infix Expression: ";
getline(cin, input);
infixToPostfix(input);
}
int main()
{
GetInput();
}

Related

infix to postfix program not producing the correct output

#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <iomanip>
using namespace std;
class Stack {
public:
string stack[100][1];
int size;
Stack() { size = 0; }
~Stack() {};
void push(string data) {
stack[size][0] = data;
size += 1;
}
bool empty() {
if (size == 0)
{
return true;
}
else
{
return false;
}
}
string pop() {
size -= 1;
return stack[size][0];
}
string top() {
if (empty())
cout << "Stack is empty";
return stack[size - 1][0];
}
};
int pre(char op)
{
switch (op)
{
case '(': case ')': return 0;
case '+': case '-': return 1;
case '*': case '/': return 2;
}
return -1;
}
vector<string> infix_to_postfix(const vector<string>& expr) {
vector<string> postfix;
string op;
Stack st;
for (int i = 0; i < expr.size(); i++) {
if (expr[i][0] == '+' || expr[i][0] == '-' || expr[i][0] == '*' || expr[i][0] == '/') {
while (!st.empty()) {
op = (st.top()[0]);
if (pre(expr[i][0]) <= pre(op[0]))
postfix.push_back(st.pop());
else break;
}
postfix.push_back(expr[i]);
}
else if (expr[i][0] == '(') {
st.push(expr[i]);
}
else if (expr[i][0] == ')') {
while (!st.empty()) {
op = st.pop();
if (op[0] == '(') break;
else {
postfix.push_back(op);
}
}
}
else {
postfix.push_back(expr[i]);
}
}
return postfix;
}
int main() {
auto expr = infix_to_postfix({ "(", "2", "+", "3", ")", "*", "7" });
for (auto& elem : expr)
{
std::cout << elem << ", ";
}
std::cout << "\n";
return 0;
}
This program is supposed to convert from infix to postfix but it is not producing the correct output. I'm expecting the output to be:
2, 3, +, 7, *,
but the output is
2, +, 3, *, 7,
You have two issues.
When handling an operator, after popping the lower precedence operators you need to push the new operator onto the stack rather than adding it to the result:
if (expr[i][0] == '+' || expr[i][0] == '-' || expr[i][0] == '*' || expr[i][0] == '/') {
while (!st.empty()) {
op = (st.top()[0]);
if (pre(expr[i][0]) <= pre(op[0]))
postfix.push_back(st.pop());
else break;
}
st.push(expr[i]);
}
At the end of the function you need to pop any remaining operators off the stack:
while (!st.empty())
{
postfix.push_back(st.pop());
}
return postfix;

How can i print this caculation? -DS stack question

this is data structure (stack) question. in c++. (no use STL)
i want input Infix Formula file(txt, if there is not file, input is user's typing.)
and convert Postfix Formula, then caculate formula.
how can i input Postfix Formula in caculate fuction ?
i try make file and read file, but is not work. (i try change endl position(delete), also not work.)
ArrayStack.h
#include <iostream>
#include <cstdlib>
#define _CRT_SECURE_NO_WARNINGS
using namespace std;
inline void error(const char *message)
{
cout << message << endl;
exit(1);
}
const int MAX_STACK_SIZE = 20;
class ArrayStack
{
private:
int top;
int data[MAX_STACK_SIZE];
public:
ArrayStack()
{
top = -1;
}
~ArrayStack()
{
}
bool isEmpty()
{
return top == -1;
}
bool isFull()
{
return top == MAX_STACK_SIZE - 1;
}
void push(int e)
{
if (isFull())
error("스택 포화 에러");
data[++top] = e;
}
int pop()
{
if (isEmpty())
error("스택 공백 에러");
return data[top--];
}
int peek()
{
if (isEmpty())
error("스택 공백 에러");
return data[top];
}
void display()
{
printf("[스택 항목의 수 = %2d] ==> ", top + 1);
for (int i = 0; i < top; i++)
printf("<%2d>", data[i]);
printf("\n");
}
};
pg1_stack.cpp
#pragma warning(disable:4996)
#include "ArrayStack.h"
#include <string.h>
#include <fstream>
inline static int precedence(char op)
{
switch (op) {
case '(': case ')': return 0;
case '+': case '-': return 1;
case '*': case '/': return 2;
}
return -1;
}
void infixToPostfix(FILE *fp = stdin)
{
char c, op;
double val;
ArrayStack stack;
ofstream os;
os.open("stack_Data.txt");
while ((c = getc(fp)) != '\n')
{
if ('0' <= c && c <= '9')
{
ungetc(c, fp);
fscanf_s(fp, "%lf", &val);
printf("%4.1f ", val);
os << val;
}
else if (c == '(')
stack.push(c);
else if (c == ')')
{
while (!stack.isEmpty())
{
op = stack.pop();
if (op == '(') break;
else
printf("%c ", op);
os << op;
}
}
else if (c == '+' || c == '-' || c == '*' || c == '/')
{
while (!stack.isEmpty())
{
op = stack.peek();
if (precedence(c) <= precedence(op))
{
printf("%c ", op);
os << op;
stack.pop();
}
else break;
}
stack.push(c);
}
}
while (!stack.isEmpty()) {
char c2 = stack.pop();
os << c2;
printf("%c ", c2);
}os << endl;
os.close();
printf("\n");
}
double calcPostfixExpr(const char *filename)
{
FILE *fp = fopen(filename, "r");
if (fp == NULL)
error("Error: 파일 존재하지 않습니다.\n");
char ch;
ArrayStack stack;
while ((ch = getc(fp)) != '\n')
{
if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
{
double right = stack.pop();
double left = stack.pop();
switch (ch) {
case '+':
stack.push(left + right);
break;
case '-':
stack.push(left - right);
break;
case '*':
stack.push(left * right);
break;
case '/':
stack.push(left / right);
break;
}
}
else if ('0' <= ch && ch <= '9')
{
ungetc(ch, fp);
double val;
fscanf_s(fp, "%lf", &val);
stack.push(val);
}
}
fclose(fp);
return stack.pop();
}
void main() {
infixToPostfix();
double res = calcPostfixExpr("stack_Data.txt");
printf("%f", res);
system("Pause");
}
this is before try make file and read file way
#pragma warning(disable:4996)
#include "ArrayStack.h"
#include <string.h>
#include <fstream>
inline static int precedence(char op)
{
switch (op) {
case '(': case ')': return 0;
case '+': case '-': return 1;
case '*': case '/': return 2;
}
return -1;
}
void infixToPostfix(FILE *fp = stdin)
{
char c, op;
double val;
ArrayStack stack;
while ((c = getc(fp)) != '\n')
{
if ('0' <= c && c <= '9')
{
ungetc(c, fp);
fscanf_s(fp, "%lf", &val);
printf("%4.1f ", val);
}
else if (c == '(')
stack.push(c);
else if (c == ')')
{
while (!stack.isEmpty())
{
op = stack.pop();
if (op == '(') break;
else
printf("%c ", op);
}
}
else if (c == '+' || c == '-' || c == '*' || c == '/')
{
while (!stack.isEmpty())
{
op = stack.peek();
if (precedence(c) <= precedence(op))
{
printf("%c ", op);
stack.pop();
}
else break;
}
stack.push(c);
}
}
while (!stack.isEmpty()) {
char c2 = stack.pop();
printf("%c ", c2);
}
printf("\n");
}
double calcPostfixExpr(FILE* fp = stdin)
{
char ch;
ArrayStack stack;
while ((ch = getc(fp)) != '\n')
{
if (ch == '+' || ch == '-' || ch == '*' || ch == '/')
{
double right = stack.pop();
double left = stack.pop();
switch (ch) {
case '+':
stack.push(left + right);
break;
case '-':
stack.push(left - right);
break;
case '*':
stack.push(left * right);
break;
case '/':
stack.push(left / right);
break;
}
}
else if ('0' <= ch && ch <= '9')
{
ungetc(ch, fp);
double val;
fscanf_s(fp, "%lf", &val);
stack.push(val);
}
}
return stack.pop();
}
void main() {
infixToPostfix();
system("Pause");
}

Infix to Postfix using Stacks w/ Professor's Algorithm

Been scratching my head for hours already and I have no clue what my mistake is. I'm following my professor's derived algorithm step by step and I don't know why it isn't working properly.
Here's the derived Algorithm:
Here's the code that I tried to make:
#include <iostream>
#include "ecpe202.h"
#define Max 100
using namespace std;
int getICP(char x){
if (x == ')'){
return 0;
}
else if (x == '^'){
return 4;
}
else if (x == '*' || x == '/'){
return 2;
}
else if (x == '+' || x == '-'){
return 1;
}
else if (x == '('){
return 4;
}
}
int getISP(char x){
if (x == ')'){
return 0;
}
else if (x == '^'){
return 3;
}
else if (x == '*' || x == '/'){
return 2;
}
else if (x == '+' || x == '-'){
return 1;
}
else if (x == '('){
return 0;
}
}
bool isOperator(char ch){
if (ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == '^' || ch == '*' || ch == '(' || ch == ')'){
return (true);
}
else{
return (false);
}
}
int main(){
char infix[Max];
char ch;
int length;
myQueue que;
myStack stk;
createQ(que);
createS(stk);
cout << "Enter an infix Expression: ";
cin >> infix;
cout << endl << endl;
cout << "The postfix Expression: ";
length = strlen(infix);
for (int i = 0; i < length; i++){
addQ(que, infix[i]);
}
while (!isEmptyQ(que)){
ch = retrieveQ(que);
//start of infix to postfix algo
//1. push
if (ch == '('){
pushS(stk, ch);
}
//2. if scanned is operand
if (!isOperator(ch)){
cout << ch;
}
else{
//2.1 push if...
if (isEmptyS(stk) || getICP(ch) > getISP(topS(stk)) || topS(stk) == '('){
pushS(stk, ch);
}
//2.2. pop all operators
else{
while(!isEmptyS(stk) && getISP(topS(stk)) >= getICP(ch) || topS(stk) == '('){
cout << popS(stk);
}
}
pushS(stk, ch);
}
//3. If scanned ')'
bool loop = true;
if (ch == ')'){
do{
if (ch == '('){
loop = false;
}
else{
cout << popS(stk);
}
}while(loop == true);
}
//repeat 1-3
}
cout << endl;
}
For the ecpe202.h:
#include<dos.h>
#include<windows.h>
#define FOREVER true
#define MAXSTACK 100
#define MAXQUEUE 100
using namespace std;
struct myStack{
int tos;
char s[MAXSTACK];
};
struct myQueue{
int head, tail, q[MAXQUEUE];
};
//STACK
void createS(myStack &S){
S.tos=-1;
}
void pushS(myStack &S, char item){
S.s[++S.tos] = item;
}
char popS(myStack &S){
return(S.s[S.tos--]);
}
char topS(myStack S){
return (S.s[S.tos]);
}
bool isFullS(myStack S){
if(S.tos == MAXSTACK - 1)
return true;
return false;
}
bool isEmptyS(myStack S){
if (S.tos == -1)
return true;
return false;
}
//QUEUE
void createQ(myQueue &Q){
Q.head = 0;
Q.tail = 0;
}
void addQ(myQueue &Q, char item){
Q.q[Q.tail++] = item;
Q.tail %= MAXQUEUE;
}
char retrieveQ(myQueue &Q){
char temp;
temp = Q.q[Q.head++];
Q.head %= MAXQUEUE;
return temp;
}
bool isFullQ(myQueue Q){
if (Q.tail == MAXQUEUE)
return true;
return false;
}
bool isEmptyQ(myQueue Q){
if (Q.tail == Q.head)
return true;
return false;
}
//GOTOXY
void gotoxy(int x, int y){
COORD coord;
coord.X = x;
coord.Y = y;
SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
}
void clrscr(){
system("CLS");
}
The output that my code:
What seems to be wrong in my program? tried re-reading it a couple of times and I still can't fix it.

Conversion of infix to postfix: stack is not recognized error

I am a beginner using the stack so I been trying to do different exercises on it. I'm trying to convert infix->postfix. The xcode debugger says "Use of class template 'stack'requires template arguments'. Here is my code.
#include<iostream>
#include<stack>
#include<string>
using namespace std;
bool IsOperand(char ch)
{
if ((ch >= '0' && ch <= '9') || (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')) {
return true;
}
return false;
}
bool IsOperator(char C)
{
if (C == '+' || C == '-' || C == '*' || C == '/' || C == '^') {
return true;
}
return false;
}
bool IsLeftParenthesis(char ch)
{
if (ch == '(') {
return true;
}
return false;
}
bool IsRightParenthesis(char ch)
{
if (ch == ')') {
return true;
}
return false;
}
bool Flag(char ch)
{
if (!IsOperand(ch) || !IsOperator(ch) || !IsLeftParenthesis(ch) || !IsRightParenthesis(ch)) {
return false;
}
return true;
}
int IsRightAssociative(char op)
{
if (op == '^') {
return true;
}
return false;
}
int GetOperatorWeight(char op)
{
int weight = -1;
switch (op) {
case '+':
case '-':
weight = 1;
break;
case '*':
case '/':
weight = 2;
break;
case '^':
weight = 3;
break;
}
return weight;
}
bool HasHigherPrecedence(char op1, char op2)
{
int op1Weight = GetOperatorWeight(op1);
int op2Weight = GetOperatorWeight(op2);
// If operators have equal precedence, return true if they are left associative.
// BUT REMEMBER...return false, if right associative.
// if operator is left-associative, left one should be given priority.
if (op1Weight == op2Weight) {
if (IsRightAssociative(op1)) {
return false;
}
else {
return true;
}
}
return op1Weight > op2Weight ? true : false;
}
string InfixToPostfix(string expression)
{
stack S;
string postfix = "";
for (auto& elem : expression) {
if (Flag(elem)) {
continue;
}
// If character is operator, pop two elements from stack, perform operation and push the result back.
else if (IsOperator(elem)) {
while (!S.empty() && S.top() != '(' && HasHigherPrecedence(S.top(), elem)) {
postfix += S.top();
S.pop();
}
S.push(elem);
}
else if (IsOperand(elem)) {
postfix += elem;
}
else if (elem == '(') {
S.push(elem);
}
else if (elem == ')') {
while (!S.empty() && S.top() != '(') {
postfix += S.top();
S.pop();
}
S.pop();
}
}
while (!S.empty()) {
postfix += S.top();
S.pop();
}
return postfix;
}
int main()
{
// std::string expression = "54/(5^2)+(6^2^3)";
std::string expression = "A+(BC-(D/E^F)G)H";
std::string postfix = InfixToPostfix(expression);
std::cout << "Output = " << postfix << "\n";
}
Here specificially where the error is happening.
string InfixToPostfix(string expression)
{
stack S;
It says
Stack S -> Use of class template 'stack'requires template arguments'
Stack is a container, you need to specify the type of the container like:
stack <int> S;
or in you case it is stack of char:
stack <char> S;

Infix to Postfix notation C++ [duplicate]

This question already has answers here:
Convert from an infix expression to postfix (C++) using Stacks
(6 answers)
Closed 9 years ago.
Hello Stack I'm curently atempting to write a RPN converter and I'm new to C++. But I'm running into problems. Hopefully I can explain the problems in detail. Im using an array for stacking my operators. Lets use the example "5 + 8" When I get down to:
else if(infix[i] == '+' or infix[i] == '-' or infix[i] == '*' or infix[i] == '/' or infix[i] == '^'){
while(isp(stack1.top()) >= icp(infix[i])){
postfix += stack1.pop();
}
if(isp(stack1.top()) < icp(infix[i])){
stack1.push(infix[i]);
}
For some reason it will push the operator onto the stack but then it wont add the operator to the postfix string variable that im adding my elements too. the out put woul be like "5 8" I looked at my pop function and that seems to be correct but im stumped. if you can lead me in the right direction that would be great.
This is my full code:
#include <iostream>
#include <string>
#define DEFAULT_SIZE 100
using namespace std;
class Stack{
private:
char *array;
int tos, capacity;
public:
//constructors
Stack();
//Destructor
~Stack();
//Methods
void push(char a);
char pop();
char top();
int get_size();
bool is_empty();
bool is_full();
void display();
};
Stack::Stack(){
array = new char[DEFAULT_SIZE];
tos = 0;
capacity = DEFAULT_SIZE;
}
Stack::~Stack(){
delete[] array;
}
void Stack::push(char a){
if(!is_full())
array[tos++] = a;
}
char Stack::pop(){
return array[--tos];
}
char Stack::top(){
return array[tos];
}
int Stack::get_size(){
return tos;
}
bool Stack::is_empty(){
if(tos == 0)
return true;
else
return false;
}
bool Stack::is_full(){
if(tos == capacity)
return true;
else
return false;
}
void Stack::display(){
if (tos == 0)
cout<<"The stack is empty"<<endl;
else{
for (int i=0; i<tos;i++)
cout<<array[i]<<" ";
cout<<endl;
}
}
int isp(char a){
if(a == '^'){
return 3;
}
else if (a == '*' or a == '/'){
return 2;
}
else if(a == '+' or a == '-'){
return 1;
}
else if(a == '('){
return 0;
}
else
return -1;
}
int icp(char a){
if(a == '^'){
return 4;
}
else if (a == '*' or a == '/'){
return 2;
}
else if(a == '+' or a == '-'){
return 1;
}
else if(a == '('){
return 4;
}
}
int main(){
string infix, postfix;
Stack stack1;
cout << "This is a Infix to Postfix Expression converter." << endl;
cout << "Enter your Infix Expression: ";
cin >> infix;
stack1.push('#');
for(int i=0;i<infix.length();i++){
if(isdigit(infix[i]) or isalpha(infix[i])){
postfix += infix[i];
}
else if(infix[i] == '+' or infix[i] == '-' or infix[i] == '*' or infix[i] == '/' or infix[i] == '^'){
while(isp(stack1.top()) >= icp(infix[i])){
postfix += stack1.pop();
}
if(isp(stack1.top()) < icp(infix[i])){
stack1.push(infix[i]);
}
}
}
cout << postfix;
return 0;
}
Also if you know anygood resource sites on C++ RPN converter feel free to share because it would be a very big help! Im going off a random algo. that I found on google.
With your example, you're just pushing the "+" sign on the stack, but you never pop it because after processing the symbol "8", you've left the for loop. I think you need another while loop to empty your stack at the end.
for(int i=0;i<infix.length();i++){
if(isdigit(infix[i]) or isalpha(infix[i])){
postfix += infix[i];
}
else if(infix[i] == '+' or infix[i] == '-' or infix[i] == '*' or infix[i] == '/' or infix[i] == '^'){
while(isp(stack1.top()) >= icp(infix[i])){
postfix += stack1.pop();
}
if(isp(stack1.top()) < icp(infix[i])){
stack1.push(infix[i]);
}
}
}
// Fetch the remaining operators from the stack
while(!stack1.is_empty()){
postfix += stack1.pop();
}
cout << postfix;
Beware of bugs, as I couldn't test this code myself.