Two pointers is a very simple and useful algorithm and actually using it is optional but, using it will make your algorithm easier and more simple.

but now, how to use it ? I think its good for you to look at https://www.geeksforgeeks.org/two-pointers-technique/ too. it'll be useful:blush:

so let go ...

As it's shown by its name this algorithm use two pointers on an array(or two arrays) which initially are located at position x, y . then if CONDITION1 move pointer1 one to left/right and if CONDITION2 move pointer2 one to left or right.

now let's switch to code.

QUESTION ANSWER SPOIL DANGER ================== to help you understand more I'll use one easy question and analyze them together.

QUESTION 1:( 1968B - Prefiquence )

so it says that we have two binary strings a,_ b_ and we want to find the maximum number of k which is the first k consecutive elements of a that are subsequence of b.

so what we do is we initially locate p1 (first pointer) at first of a and p2 (second pointer) at first of b.

if a[p1] == b[p2] : p1 ++
p2 ++

now p1 is the number of k.:sunglasses:

#include <bits/stdc++.h>
using namespace std;
int main(){
    int t; cin >> t;
    while(t--){
        int n, m; string a, b; cin >> n >> m >> a >> b;
        int p1=0, p2=0;
        while (p2 < m){
            if(b[p2] == a[p1]) p1 ++;
            p2 ++;
        }
        cout << p1 << "\n";
    }

this are some more easy questions that may help you: 1873D - 1D Eraser 1972A - Contest Proposal 1851B - Parity Sort

I hope you enjoyed reading this article.:blush: MAY THE CODE BE WITH YOU!:pray: