CODEWITHSUNDEEP
c++stringloops
Chaitanya
Chaitanya

Reputation: 15

Why is is showing error in rotating the strings of larger length?

my code

#include<bits/stdc++.h>
using namespace std;

int main() {

    int n ;
    cin >> n;


    string s1 , s2 , s3;
    cin >> s1 >> s2;

    string s = s1 + s1;

    int count = 0;

    for (int i = 0 ; s3 != s2 ; i++) {

        // int a = s.find()

        s3 = s.substr( i , s1.length() );

        count++;
    }

    cout << count - 1;

    return 0;
}

In this when I try to rotate the small sized string it is working fine but when I tried with some large length string it is showing error

terminate called after throwing an instance of 'std::out_of_range'
what():  basic_string::substr: __pos (which is 227) > this->size() (which is 226)

I'm not understanding what is happening as with the string length of 20 or 30 it is working fine but when then string length is over the 110 it is showing this type of error.

Also this testcase is showing error

113 ndafmffmuuwjzqpquwjhuftohawpfegsjvnxwipwqlswvawogjuyiqtzsgpwgosegmuuhpzwchejuiitumyescxxyecnsatcbfpseqzowvdjyvchg zqpquwjhuftohawpfegsjvnxwipwqlswvawogjuyiqtzsgpwgosegmuuhpzwchejuiitumyescxxyecnsatcbfpseqzowvdjyvchgavqnonmkwgqp

Upvotes: 0

Views: 83

Answers (1)

Marek R
Marek R

Reputation: 38062

This is quite simple your for loop has condition which is never false for this input. So you are increasing i beyond size of s (double of size of s1).

Note common part of this two strings is: zqpquwjhuftohawpfegsjvnxwipwqlswvawogjuyiqtzsgpwgosegmuuhpzwchejuiitumyescxxyecnsatcbfpseqzowvdjyvchg. Difference is:

  • s1 has in front: ndafmffmuuwj
  • s2 has in backL: avqnonmkwgqp

So s1 is not rotation of s2 that is why codition in for is never fasle.

This is the reason std::basic_string::substr throws an exception.

Live demo.
Some fix.

And here is better way to do it.

Upvotes: 1

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