Help me in solving LTB11121 problem

My issue

plz explain its sol or give me an approach

My code

#include <bits/stdc++.h>
#define ll long long int
using namespace std;

int main() {
	// your code goes here
	ll t;
	cin>>t;
	while(t--){
	    ll n;
	    cin>>n;
	    string s,str;
	    cin>>s>>str;
	    ll diff=0;
	    for(ll i=0;i<n;i++){
	        if(s[i]!=str[i])diff++;
	    }
	    if()
	}
	
	return 0;
}

Problem Link: LTB11121 Problem - CodeChef

//ladchat supremacy

#include <bits/stdc++.h>

using namespace std;

#define ll long long

#define MAX 1000000007

int main() {

	ll t;

	cin>>t;

	

	while(t--){

	    ll n;

	    cin>>n;

	    string s,ans;

	    cin>>ans;

	    //string ans;

	    cin>>s;

	    vector<ll>need(n,0);

	    for(ll i=0;i<n;i++)if(s[i]!=ans[i])need[i]++;

	    ll first,last;

	    first=last=-1;

	    for(ll i=0;i<n;i++){

	        if(s[i]!=ans[i]){

	            first=i;

	            break;

	        }

	    }

	    for(ll i=n-1;i>=0;i--){

	        if(s[i]!=ans[i]){

	            last=i;

	            break;

	        }

	    }

	    

	    ll seg=0;

	    ll it=0;

	    while(it<n){

	        if(s[it]!=ans[it]){

	            while(it<n && s[it]!=ans[it])it++;

	            seg++;

	        }

	        else it++;

	    }

	    //cout<<first<<" "<<last<<" ";

	    //cout<<seg<<" ";

	    if(seg==1){

	        

	        ll fin=0;

	        fin=((first-0)+(n-1-last))*2+(last-first)*2; // first and last belong to same segment

	        cout<<fin<<endl;

	    }

	    else if(seg==0){

	        cout<<(n*(n+1)/2)<<endl;

	    }

	    else if(seg>2)cout<<0<<endl;

	    else{

	        cout<<6<<endl;

	    }

	}

	return 0;

}

include <bits/stdc++.h>
define ll long long int
using namespace std;

int main() {
// your code goes here
ll t;
cin >> t; // Read the number of test cases

while (t--) { // Iterate through each test case
    ll n;
    cin >> n; // Read the length of the strings

    string s, str;
    cin >> s >> str; // Read two strings of length n

    ll diff = 0;
    for (ll i = 0; i < n; i++) {
        if (s[i] != str[i])
            diff++; // Count the number of positions where the strings differ
    }

    // Now, you need to add some code here to determine the result based on the value of 'diff'.

    // For example, you can print "YES" if diff is 0, indicating that the strings are identical.
    // Or you can print "NO" if diff is not 0, indicating that the strings are different.

    // Here's an example:
    if (diff == 0) {
        cout << "YES" << endl;
    } else {
        cout << "NO" << endl;
    }
}

return 0;

}
The code reads the number of test cases t, and for each test case, it reads two strings s and str of length n. It then calculates the number of positions where these strings differ and stores it in the diff variable. Finally, you need to add code to determine the result based on the value of diff.

In the example code I provided, it prints “YES” if diff is 0 (indicating the strings are identical) and “NO” otherwise. You can modify this part based on the specific problem requirements.