Whats the problem in my code

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C++

#include <stdio.h>
#include <string.h>

int main()
{
    int n,flag=0,p;
    scanf("%d",&n);
    while(n--){
        int j=0;
        char s[10000];
        scanf("%s",&s);
        j=strlen(s);

        for(int i=1;i<=j/2;i++){

            if(s[i]==s[j-i+1])
            flag++;
            p=i;
            }
        if(flag==p)
            printf("palindrome");
            else
        printf("not");

    }
}

[edit]Code block added - OriginalGriff[/edit]

What I have tried:

i m trying to check palindrome string.

Posted 26-Aug-17 0:56am

jatinp510

Updated 26-Aug-17 3:38am

OriginalGriff

v2

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Richard MacCutchan 26-Aug-17 7:18am

What is the question?

2 solutions

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OriginalGriff · Answer 1 · 2017-08-26T01:40:00

Solution 1

Well, it's pretty simple - and if you had used the debugger, you would have spotted it pretty quickly.

Start with a couple of hints:
1) What is the index of the first element of an array?
2) What is operator precedence going to do to this:

C++

j-i+1

Will it be evaluated as

C++

j-(i+1)

Or as

C++

(j-i)+1

Does it matter?
3) Does (1) have any effect on the value of p?
4) What is the value of flag the second time you go round the outer loop?

Instead of checking like that, add a variable called isPalindrome, and set it to 1 (this is C for "true") outside the inner loop.
Inside the loop, if you find a single non-match, set it to 0 (this is C for "false")

After the loop, check it, and it tells you if it's a palindrome...

Posted 26-Aug-17 1:40am

OriginalGriff

Comments

jatinp510 27-Aug-17 1:21am

thnk u soo much

OriginalGriff 27-Aug-17 1:40am

You're welcome!

jatinp510 27-Aug-17 2:18am

//in this code i have checked for whether this is palindrome and if its palindrome it will check whwther its odd or even
//suggest me a better code to improve my skills

#include <stdio.h>
#include <string.h>

int main()
{
int n,p,i;
scanf("%d",&n);
while(n--){
int flag=0,type=0;
int j=0;
char s[100000];
scanf("%s",&s);
j=strlen(s);
if(j==1){
printf("YES ODD\n");
}
else{

if(j%2==0){
type=1;
}

for(int i=0;i<j/2;i++){
if(s[i]==s[j-i-1])
flag++;
p=i;}
if(flag==(p+1)&&type==1)
printf("YES EVEN\n");
else if(flag==(p+1)&&type==0)
printf("YES ODD\n");
else
printf("NO\n");

}}
}

OriginalGriff 27-Aug-17 2:30am

Perhaps you should have spent longer thinking about the task rather than rushing into code? That's ... um ... pretty poor, if I'm honest.

jatinp510 27-Aug-17 3:15am

sir i m a begineer...
plzz.. give me some precious suggestions.. :)

OriginalGriff 27-Aug-17 3:36am

OK: stop rushing into code.
Thinking about the problem and designing a solution first makes your whole life easier: like planning a route in your car before you set off, instead of getting in the car and rushing off in hopefully-right direction. Making sure you have enough fuel, your credit cards or what-not, the wife, the kids with you before you set off.

At the moment, you are looking at the task and rush in to type - and you end up with confused code that sort of works, but doesn't qite do it, and then you hack it a bit, then some more, and you end up with something that still doesn't quite work but you don't understand and can't easily modify.

So ignore that lot, back up and read the problem fully - then design a way to do it ignoring code completely, before translating that into code.

There are three stages here:
1) Get input.
2) Check if it's a palindrome.
3) Check if it's "odd" - which I assume means is the length odd or even.
You are mixing them up too much, and not making your life easy as a result.

I'm not going to do the code for you - it's your homework, and doing it is how you learn this stuff - but you can do it pretty easily if you sit down and think first! Have a go - it's not a complicated task, honest!

jatinp510 27-Aug-17 4:24am

thnk u... once again :)

OriginalGriff 27-Aug-17 4:40am

You're welcome!

Patrice T · Answer 2 · 2017-08-26T03:38:00

First of all, use proper indentation, it help you reading the code, it helps strangers reading your code.

C++

#include <stdio.h>
#include <string.h>

int main()
{
    int n,flag=0,p;
    scanf("%d",&n);
    while(n--){
        int j=0;
        char s[10000];
        scanf("%s",&s);
        j=strlen(s);

        for(int i=1;i<=j/2;i++){

            if(s[i]==s[j-i+1])
                flag++;
            p=i;
        }
        if(flag==p)
            printf("palindrome");
        else
            printf("not");

    }
}

C arrays are 0 based, which means that the first char in s is s[0]. You start checking on second char.

There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

Whats the problem in my code

2 solutions

Solution 1

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