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Given a string S with length N. Choose an integer K and two non-empty subsequences A and B of characters of this string, each with length K, such that:

>> A=B, i.e. for each valid i, the i-th character in A is the same as the i-th character in B.

>> Let's denote the indices of characters used to construct A by a1,a2,…,aK, i.e.

A=(Sa1,Sa2,…,SaK). Similarly, let's denote the indices of characters used to construct B by b1,b2,…,bK.

>>If we denote the number of common indices in the sequences a and b by M, then M+1≤K.

What is the maximum value of K such that it is possible to find sequences A and B which satisfy the above conditions.

Input
>> The first line of the input contains a single integer T denoting the number of test cases. The description of T test cases follows.

>>The first line of each test case contains a single integer N.

>>The second line contains a single string S with length N.

Output pattern
For each test case, print a single line containing one integer ― the maximum K, or 0 if there is no solution.

The code i tried below works for whatever input i give. But still whenever I submit the code it shows WA

What I have tried:

C++
```#include <iostream>
#include <vector>
#include <map>
#include <string>
#include <algorithm>
using namespace std;
#define boost ios::sync_with_stdio(0); cin.tie(0)

int findLongestRepeatingSubSeq(string s){
int len = s.length();
if(len<=1)return 0;
vector<vector<int>>dp(len+1,vector<int>(len+1,0));

for(int i=1;i<=len;i++){
for(int j=1;j<=len;j++){
if(s[i-1]==s[j-1] && i!=j){
dp[i][j] = dp[i-1][j-1]+1;
}else{
dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
}
}
}

return dp[len][len];
}

int main(){
boost;
int t;
cin >> t;
while(t--)
{
int n;
cin >> n;
string str;
cin >> str;
cout << findLongestRepeatingSubSeq(str) << endl;
}
}```

I don't know what I'm doing wrong. So I really appreciate any help on this one
Posted
Updated 10-Dec-19 0:26am
v5

## Solution 1

Compiling does not mean your code is right! :laugh:
Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:
<pre lang="text">Input Expected output Actual output
1 2 1
2 4 4
3 6 9
4 8 16Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:
C#
```int Double(int value)
{
return value * value;
}```

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

v2

## Solution 2

Try These test Case
4
4
anxa
6
ababcb
4
abcd
1
a
Output should be
1
4
0
0