unsigned int value not giving correct result - c++

following program should print "error" but its printing success.why?
#include<iostream>
using namespace std;
int main()
{
unsigned int a;
a=-10;
if(a == -10)
cout << "success" ;
else
cout << "error" ;
return 0;
}

The conversion for comparison makes them equal again. But it should cause the compiler to emit a warning.

Related

Segmentation Fault on Recursion

I want to count the number of recursivily call that has a number in the Collatz Sequence. But for such a bigger number for example 4565458458
#include <cstdlib>
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int f(int value){
if(value==1) return 1;
else if(value%2 == 0) return value/2;
else return 3*value+1;
}
int g(int value){
if(value == 0) return 0;
if (f(value)==1) return 1;
return 1 + g(f(value));
}
int main(int argc, char *argv[]){
int nSteps=0;
istringstream iss(argv[1]);
int;
if(!(iss >> num).fail()){
if(num < 0) cout << "0" << endl;
else{
nSteps = g(num);
cout << "Result: " << nSteps << endl;
}
}
else{
cout << "Incorrect line paramaters: ./g n" << endl;
}
return 0;
}
Your program will use a lot of stack-memory for large inputs.
In addition f should have the same input and output type (originally it had "unsigned long long" as input and int as output), or the result will be wrong.
I would advise you to first rewrite g without recursion, and if that works try to investigate how to get g to be efficient with tail-recursion (the current variant does probably not support it).
Using a debugger as others suggested is also good, especially if it crashes before calling 'g'.
Finally 'num<0' does not make sense for an unsigned 'num'.

Printing all palindrome numbers in a given range

I'm trying to write a program that would print all palindrome in range [a, b]. I've written this so far, but nothing is printed after I input the values for a, b. What is missing?
#include "stdafx.h"
#include <iostream>
using namespace std;
int t = 0, rmd, z, a, b;
int reverse() {
while (z != 0) {
rmd = z% 10;
t = t * 10 + rmd;
z/= 10;
}
return t;
}
int palin() {
if (a == reverse()) {
return 1;
}
else
return 0;
}
int main() {
cout << "a: "; cin >> a;
cout << "b: "; cin >> b;
while (a <= b) {
z = a;
if (palin())
cout << a << endl;
a++;
}
system("pause");
return 0;
}
The problem is that the variable t is not local to your reverse() function. Its value survives to the following invocation, so the result of reverse becomes junk unrelated to the actual call.
You need to make t local to reverse() in order to fix this problem.
In general, it is a good idea to develop a habit of declaring your variables in the innermost scope to which they could belong without breaking your code. In this case, this would be the scope of reverse() function for t, and the scope of main for the remaining variables; palin should take a as its parameter.
Your use of variables is what is confusing you. The actual issue is not setting t to zero every time you call reverse, but you should think about how you use variable scoping and what functions actually do. Right now you have 2 procedures, that perform actions on global data. Instead try to formulate the problem using functions that accept arguments, and return a result.
#include <iostream>
using namespace std;
int reverse(int z) {
int t = 0;
int rmd;
while (z != 0) {
rmd = z % 10;
t = t * 10 + rmd;
z/= 10;
}
return t;
}
int palin(int z) {
return z == reverse(z);
}
int main() {
int a, b;
cout << "a: "; cin >> a;
cout << "b: "; cin >> b;
while (a <= b) {
if (palin(a)) {
cout << a << endl;
}
a++;
}
system("pause");
return 0;
}

no match for operator '<<' Can someone aid with void function error? [c++]

This post treats the same error, but the poster isn't have trouble with a void function.
This post concerns the "void" type of function, but the poster is advised to change the function type to "string", which does not help my case.
My code executes fine, except for a literal "0" at the end of the output. When I change the function type to "void", I am met with the above error.
I have been through the tutorial on this numerous times, and have searched thoroughly, yet have been unable to resolve this issue.
//my code
#include <iostream>
using namespace std;
int intervalcountdown (int a, int b) {
for(a; a>0; a = a - b) {
cout << a;
if(a<=b) {
break;
}
cout << ",";
}
cout << ".";
return 0;
}
int main () {
cout << intervalcountdown(20,3);
return 0;
}
Just don't print what you don't want.
#include <iostream>
using namespace std;
void intervalcountdown (int a, int b) { // change return type to void
for(; a>0; a = a - b) { // meaningless a is removed
cout << a;
if(a<=b) {
break;
}
cout << ",";
}
cout << ".";
// remove the return statement because the return type is now void
}
int main () {
intervalcountdown(20,3); // remove extra printing
return 0;
}

No output when merge function is called

I have a doubt in the following code. Can somebody please explain.
using namespace std;
#define INT_SIZE 32
#define R 4
#define C 4
#define N 4
#include <iostream>
#include <stdio.h>
#include<stdlib.h>
#include<math.h>
#include<limits.h>
#include<stack>
#include<vector>
#include<algorithm>
struct interval{
int start;
int end;
};
bool compareInterval(interval i1, interval i2)
{
return (i1.start < i2.start)? true: false;
}
int merge(vector<interval>& a, int n)
{
stack<interval> s;
sort(a.begin(), a.end(), compareInterval);
s.push(a[0]);
int i=1;
interval temp;
while(i<n)
{
temp = s.top();
s.pop();
if(temp.end > a[i].start && a[i].end > temp.end)
{
temp.end = a[i].end;
s.push(temp);
}
else if(temp.end < a[i].start)
{
s.push(temp);
s.push(a[i]);
}
i++;
}
while(s.size())
{
temp = s.top();
cout << temp.start << " ";
cout << temp.end << "\n";
s.pop();
}
return 0;
}
int main()
{
interval intvls[] = { {6,8}, {1,9}, {2,4}, {4,7} };
vector<interval> intervals(intvls, intvls+4);
for(int i=0;i<4;i++)
{cout << intervals[i].start;
} // This output is not coming when merge function is called
cout << merge(intervals, 4);
}
My doubt is "When I comment the merge function call i.e
// cout << merge(intervals, 4);
When I comment this line, then I am able to see output of cout<<intervals[i].start.
Otherwise, I am not able to see the output.
"
You are not ending your output with a newline. Try:
{cout << intervals[i].start << "\n";}
Without the newline, this output is probably getting hidden amongst all the output produced by merge().
There are few issues with this code.
s.push(a[0]); <-- Only on element is in you stack.
//s.push(a[1]).. you will have to add all other elements like this.
while(i<n)
{
temp = s.top(); <-- for second i s will be empty. Here you must check if stack is empty before getting top element.
s.pop();
}
Your first output is not printed correctly. use std::endl
cout << intervals[i].start << endl;
There is a bug in merge that leads to a segmentation fault. Due to this std::cout is not flushed. If you comment out the line with the merge call, std::cout is flushed when the program exits.

exception_handling_C++_xcode

The following code throws the exception perfectly fine in Visual Studio 2010:
#include <iostream>
#include <cmath>
using namespace std;
int perfectSquare(double sq, int nu);
int main()
{
double num;
double squareRoot;
int perfectSq;
cout << "Enter the a number: ";
cin >> num;
try
{
squareRoot = sqrt(num);
perfectSq = perfectSquare(squareRoot, num);
cout << "The square root is: " << perfectSq << endl;
}
catch(char * exceptionString)
{
cout << exceptionString;
}
cout << "BYE." << endl;
// system("PAUSE");
return 0;
}
int perfectSquare(double sq, int nu)
{
int temp = sq;
if (sq != temp) //clever test; if square root IS NOT an INT
{
throw "not a perfect square.\n";
}
else
{
return sq;
}
}
However, in Xcode, it will not resume and it keeps hitting a breakpoint in the debugger. For example if I inpute 33 (not a perfect square), the following error is displayed:
libc++abi.dylib: terminate called throwing an exception
(lldb)
It should "throw" this line: "not a perfect square." and the program should terminate (like in VS 2010). I don't want to enable exception breakpoints in Xcode as I just want the program to run all the way to the end without debugging.
Thanks to all.
What you are throwing is a string literal, which in XCode seems to be a const char*, not a char*
You are not actually throwing a char *, you are throwing a const char *. Change the exception catch to
catch(const char * exceptionString)
and it should work.
All literal strings in C++ are equivalent to pointers to a constant string, i.e. const char *.