I have a homework problem I'm having bit of a problem with, I'm asked to sort an array of C strings alphabetically using C++, sorting algo used must be bubble sort. What I've done so-far (replicated below) can sort the array but only based on the first alphabet. How do I further sort strings the strings with the same initial alphabet ?
<snipped>#arch:~/College/OOP/Lab/W3$ cat 2.cpp
/*
* Write a function which sorts an array of C strings in ascending order using bubble sort. The
* number of strings in the array and the array must be passed as parameters to the function
*/
#include <iostream>
#include <cstring>
using namespace std;
void sort(char **sar, unsigned num, unsigned len)
{
char *temp = new char[len];
if (temp == NULL)
{
cout << "\nOut-Of-Memory\n";
return;
}
for (unsigned a = 0; a < num-1; a++)
{
for (unsigned b = 0; b < ((num-a)-1); b++)
{
if (sar[b][0] > sar[b+1][0])
{
strcpy(temp, sar[b]);
strcpy(sar[b], sar[b+1]);
strcpy(sar[b+1], temp);
}
}
}
delete[] temp;
}
int main(int argc, char *argv[])
{
char **sar;
unsigned num;
unsigned len;
cout << "Number of Strings: ";
cin >> num;
cout << "Length of Strings: ";
cin >> len;
cin.ignore(); // Flush buffer to fix a bug (getline after cin).
sar = (char **) new char*[num];
if (sar == NULL)
{
cout << "\nOut-Of-Memory\n";
return -1;
}
for (unsigned i = 0; i < num; i++)
{
sar[i] = (char *) new char[len];
if (sar[i] == NULL)
{
// Let's pretend we 'know' memory management
// because obviously modern OSs are incapable
// of reclaiming heap from a quitting process..
for (unsigned j = 0; j < i; j++)
delete[] sar[j];
cout << "\nOut-Of-Memory\n";
return -1;
}
}
for (unsigned x = 0; x < num; x++)
cin.getline(&sar[x][0], 512);
sort(sar, num, len);
cout << '\n';
for (unsigned y = 0; y < num; y++)
cout << sar[y] << '\n';
for (unsigned z = 0; z < num; z++)
delete[] sar[z];
delete[] sar;
return 0;
}
change
if (sar[b][0] > sar[b+1][0])
to
if (stricmp(sar[b], sar[b+1]) > 0)
UPDATE: instead of stricmp, you can use strcasecmp
Related
so I wrote this code to reverse one of the names based on the user option the idea is to use another function to reverse and to use pointers but after trying all I could think of my code return the same name not changed the best I could do was changing the first letter of the name to a weird sign.
#include <iostream>
using namespace std;
void reverse(char* A) {
int count = 0;
char temp[10];
for (int i = 0; A[i] != NULL; i++)
count++;
for (int i = 0; A[i] != NULL; i++) {
temp[count]=A[i];
count--;
}
for (int i = 0; A[i] != NULL; i++) {
A[i] = temp[i];
}
}
int main(){
int x= 0;
int index;
char Name_list[5][10];
cout << "please enter the names of the student " << endl;
for (int i = 0; i < 5; i++) {
cin >> Name_list[i];
for (int j = 0; Name_list[i][j] != NULL; j++) {
x++;
}
while (x > 10)
{
x = 0;
cout << "you have entered more then the allowed number of characters per name enter another name " << endl;
cin >> Name_list[i];
for (int j = 0; Name_list[i][j] != NULL; j++) {
x++;
}
}
x = 0;
}
for (int i = 0; i < 5; i++) {
cout << Name_list[i] << endl;
}
cout << "please enter the index of the name you want to reverse" << endl;
cin >> index;
while (index>4||index <0)
{
cout << "you entered incorrect index please enter a number from 0 to 4 " << endl;
}
reverse(Name_list[index]);
for (int i = 0; i < 5; i++) {
cout << Name_list[i] << endl;
}
system("pause");
}
For starters such a function should return a pointer to the result string. That is it should be declared like
char * reverse( char *s );
Note: do not use variable names consisting from upper case letters.
The type int can be not large enough to store length of a string. Instead use the type size_t.
char * reverse( char *s )
{
size_t count = 0;
//...
It is totally unclear why there is present an array with the number of elements equal to the magic number 10
char temp[10];
To reverse a string there is no need to declare an auxiliary array. Such an approach is principally wrong.
In this for loop
for (int i = 0; A[i] != NULL; i++)
there is compared an object of the type char with the pointer NULL. The compiler should issue a message for such a wrong comparison. It seems you mean
for (int i = 0; A[i] != '\0'; i++)
In any case the introduced variable i in this first for loop is redundant because you already has the variable count.
As you have the array temp with the fixed size equal to 10 then the both loops after the first loop can invoke undefined behavior even if the length of the source string is equal exactly to 10.
And the result string is not zero terminated.
The function can look the following way.
char * reverse( char *s )
{
size_t count = 0;
while ( s[count] ) ++count;
for ( size_t i = 0; i < count / 2; i++ )
{
char c = s[i];
s[i] = s[count - i - 1];
s[count - i - 1] = c;
}
return s;
}
Or using standard functions you could write the function reverse the following way
#include <utility>
#include <cstring>
//...
char * reverse( char *s )
{
for ( size_t i = 0, n = std::strlen( s ); i < n / 2; i++ )
{
std::swap( s[i], s[n-i-1] );
}
return s;
}
Pay attention to that there is the standard algorithm std::reverse. Using it you could reverse a string the following way
std::reverse( s, s + std::strlen( s ) );
for (int i = 0; A[i] != NULL; i++) {
temp[count]=A[i];
count--;
}
If i goes up from 0 to 5, count goes down from 6 to 1.
Ok, a few things.
If you want do some string manipulation, look into the stdlib. Unless you are doing this for class.
Your writing everything to the end of the temp. buffer
You need to add an extra character at the end of the strings for the null byte (I think this implementation may allow for a seg. fault)
I have to find the length of an array of characters using a function that uses the pointer notation and, for some reason, I get 23 but the result should be 5.
Here is the code I built:
#include <iostream>
using namespace std;
int length(char *N)
{
int length = 0;
char* S = N;
for (; *S != '\0'; S++);
for (; *N != *S; N++)
{
length++;
}
return length;
}
int main()
{
char A[5];
char *N;
N = A;
cout << "please enter the charecters you desire" << endl;
for (int i = 0; i <=4; i++)
{
cin >> A[i];
}
cout<<length(N);
}
You don't need two loops.
And note that you have to leave a space in the array (the last element) to fill it by '\0'.
Hence by the two notes and if you want to use five characters excluding the '\0', your code will be as follows
#include <iostream>
size_t length(char *N){
size_t length = 0;
for (; *N != '\0'; N++){
length++;
}
return length;
}
int main()
{
char A[6];
std::cout << "please enter the characters you desire\n";
for (int i = 0; i < 5; i++){
std::cin >> A[i];
}
A[5] = '\0';
std::cout << length(A);
}
I want to create an array of Bitset .Binary Bitset(example "100","1010",etc)
After that I want to input from user and store in the the Bitset .
I have tried the following line but it says error.
#include<bits/stdc++>
using namespace std;
int main()
{
int n,i;
string bit_string;
cin>>n // size of Bitset array.
bitset<8> brr[n];//
for(i=0;i<n;i++)
{
cin>>bit_string;
brr[i](bit_string);
}
return 0;
}
I want to create n Bitset each of size 8 bits.Where n is given by user.
my input is binary string like.
"110010","001110"
please help
The error ocurrs because you are trying to creat a C-style array using n which is not compile-time constant. It's not possible to creat a C-style array without being n known at compile time.
The following is a good way to do what you want
Creat a std::vector<std::bitset<8>> to hold your bitset<8>s, as follows.
Note that the code ignores the excess of characters in strings iput like "111111110" (makes it "11111111") and treats any character except '1' as if it were '0' and if the input string is less than 8 characters, the code adds zeros by the default of the bitsets
#include <vector>
#include <bitset>
#include <iostream>
int main() {
int n, i;
std::string bit_string;
std::cout << "Enter the size";
std::cin >> n; // size of Bitset array.
std::vector<std::bitset<8>> brr(n);//
for (i = 0; i < n; i++) {
std::cin >> bit_string;
for (int j{}; j < bit_string.size() && j < 8; ++j) {
brr[i][j] = (bit_string[j] == '1') ? 1 : 0;
}
}
//To test
for(auto const& el :brr)
{
for(int i{}; i < 8;)
std::cout << el[i++];
std::cout<<"\n";
}
}
See Why is "using namespace std;" considered bad practice?
and
Why should I not #include <bits/stdc++.h>?
For dynamic count of the objects , Please try vector<> instead of array[]
#include<bits/stdc++>
using namespace std;
int main()
{
int n, i;
string bit_string;
cin >> n; // size of Bitset array.
vector<bitset<8>> arr; //size()=>0
arr.resize(n); //size()=>n
for (i = 0; i < n; i++)
{
cin >> bit_string;
bitset<8>& br = arr[i]; //get the i of n
int maxlen = 8;
if (bit_string.size() <= 8)
maxlen = bit_string.size();
else
cout << "warning invalid len " << bit_string.size() << " of " << bit_string << endl;
for (int j = 0; j < maxlen; j++)
{
if (bit_string[j] == '1')
br.set(j, true);
}
//cout << endl << br << endl; //output test
}
return 0;
}
If you still want to use array , please try this way
#include<bits/stdc++>
using namespace std;
int main()
{
int n, i;
string bit_string;
cin >> n; // size of Bitset array.
bitset<8>* arr = new bitset<8>[n];
for (i = 0; i < n; i++)
{
cin >> bit_string;
bitset<8>& br = arr[i]; //get the i of n
int maxlen = 8;
if (bit_string.size() <= 8)
maxlen = bit_string.size();
else
cout << "warning invalid len " << bit_string.size() << " of " << bit_string << endl;
for (int j = 0; j < maxlen; j++)
{
if (bit_string[j] == '1')
br.set(j, true);
}
//cout << endl << br << endl; //output test
}
delete[] arr; //IMPROTAND , delete the array and free memory
return 0;
}
I'm trying to write a simple program which takes an array of chars, and spits it out backwards. I know there are plenty of other ways to shorten this using a library header function, but I wanted to do it using for loops just to get used to them.
#include<stdio.h>
#include<iostream>
using namespace std;
char string1[10];
int count = 0;
char stringy[10];
void enterString()
{
cout << "please enter a string: " << endl;
cin >> string1;
}
void stringCounter(const char stringLength[])
{
//initiate for loop i = 0
//if stringLength[i] does not does not equal 'i' then carry on
//increment i
for (int i = 0; stringLength[i] != '\0'; i++)
{
count++;
}
cout << "size of string is: " << count << endl;
}
void reverseString(int arraySize, char string2[])
{
int counter = 0;
for (int i = arraySize; i >= 0; string2[i--])
{
stringy[counter] = string2[i];
counter++;
}
stringy[count] = '\0';
cout << stringy << endl;
}
int main()
{
enterString();
stringCounter(string1);
reverseString(count, string1);
return 0;
}
This is the whole program. The program is failing in function reverseString. I can't work out how to successfully read the last index of the char array string2[] and copy it into the first index of char array stringy.
One, If the user enters a string more than 10 characters long then your enterString() function will access the array out of its bound, at cin>>string1. So better to use getline to make sure you don't read more than what your array can hold.
Two, with your current implementation the reverseString() function will write to the first element of the array with the null terminator character,if the arraySize<=10, and trying to display that string will not show you anything.
This:
cin >> string1;//will try to access the array out of its bound if user give more than it can hold,i.e 10 characters
...
for (int i = arraySize; i >= 0; string2[i--])
{
stringy[counter] = string2[i];//the first iteration will put the '\0' character as the first elements of stringy
counter++;
}
Should be changed to:
cin.getline(string1,10);//make sure to get not more than 10 characters,including the null terminator
.....
for (int i = arraySize-1; i >= 0; i--)
{
stringy[counter] = string2[i];
counter++;
}
There are many mistakes in your program. If this is the exact code you are compiling then it should throw many errors.
Following might help.
#include<iostream>
using namespace std;
void reverseString(int , char *);
int stringCounter(const char );
int stringCounter(const char stringLength[])
{
int count = 0;
for (int i = 0; stringLength[i] != '\0'; i++)
count++;
cout << "size of string is: " << count << endl;
return count;
}
void reverseString(int arraySize, char string2[])
{
int counter = 0;
char stringy[100];
for (int i = arraySize - 1; i >= 0; i--)
{
stringy[counter] = string2[i];
counter++;
}
stringy[counter] = '\0';
cout << stringy << endl;
}
int main()
{
char str[] = "string";
reverseString(stringCounter(str),str);
return 0;
}
Sorry, I'm a brand new newbie to C++ and programming and I'm getting a heap corruption error. I think Im writing in unallocated memory but I can't seem to find where the error is... the program is soppuse to take user input values and rearrange them so that they would ascend. I'm also learning templates too.
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
template <typename T>
void sort(T arrayz[], int size, char ch)
{
T temporary;
int k, j;
if (ch = 'a')
{
for (k = 0; k < size; k++)
{
for (j = 0; j < size; j++)
{
temporary = arrayz[j];
arrayz[j] = arrayz[j + 1];
arrayz[j + 1] = temporary;
}
}
}
}
int main()
{
int choices, range, i;
int x;
char ch;
cout << ("Enter the amount of numbers you want =>");
cin >> x;
int *numbers = new int[x];
if (!numbers)
{
cout << "Memory Allocation error!";
cin.get();
exit(1);
}
for (int i = 0; i<x; i++)
{
cout << "Option number" << i + 1 << " =>";
cin >> numbers[i];
}
cout << "Do you want ascending or descending values (a/d) =>" ;
cin >> ch;
if (ch = 'a')
{
sort(numbers, x, ch);
}
else if (ch = 'd')
{
sort(numbers, x, ch);
}
delete[] numbers;
fflush(stdin);
cin.get();
return 0;
}
In your sort function, you are accessing elements at index j + 1. However, this is out of bounds. The valid indexes for your arrayz array are 0 through size-1. When j is size-1, j+1 is size, which accesses past the end of the array.