Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	for i := 0; i < n; i++ {
		x := getNextString(scanner)
		y := getNextString(scanner)

		fmt.Fprintln(writer, lcs(x, y))
	}

	writer.Flush()
}

func lcs(x, y string) int {
	lx := len(x)
	ly := len(y)
	dp := make([][]int, lx+1)
	for i := 0; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
	}
	for i := 0; i < lx; i++ {
		for ii := 0; ii < ly; ii++ {
			if x[i] == y[ii] {
				dp[i+1][ii+1] = dp[i][ii] + 1
				continue
			}
			dp[i+1][ii+1] = dp[i][ii+1]
			if dp[i+1][ii] > dp[i+1][ii+1] {
				dp[i+1][ii+1] = dp[i+1][ii]
			}
		}
	}
	return dp[lx][ly]
}

C++: //Longest Common Subsequence
#include <iostream>
#include <string>

using namespace std;

static const int N = 1000;

int lcs(string s1, string s2) {
    int l1 = s1.length(), l2 = s2.length();
    int dp[l1+1][l2+1];
    for(int i=0; i<l1+1; i++) dp[i][0] = 0;
    for(int j=0; j<l2+1; j++) dp[0][j] = 0;

    for(int i=1; i<l1+1; i++) {
        for(int j=1; j<l2+1; j++) {
            if(s1[i-1] == s2[j-1]) dp[i][j] = dp[i-1][j-1]+1;
            else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
        }
    }
    return dp[l1][l2];
}

int main() {
    string s1, s2;
    int n;
    cin >> n;
    for(int i = 0; i < n; i++) {
        cin >> s1 >> s2;
        cout << lcs(s1, s2) << endl;
    }
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace std;
//_____
#define rep(i,n) for(int i=0; i<(n); ++i)
#define reps(i,f,n) for(int i=(f); i<=(n); ++i)
#define outl(x) cout << (x) << '\n'
#define FAST() cin.tie(0), ios::sync_with_stdio(false)
template<class A, class B>inline bool chmax(A &a, B b){return b>a ? a=b,1 : 0;}
template<class A, class B>inline bool chmin(A &a, B b){return b<a ? a=b,1 : 0;}
//_______


int slv(string &a, string &b)
{
   const int alen = a.size();
   const int blen = b.size();
   int dp[1005][1005] = {};
   a = ' ' + a;
   b = ' ' + b;
   int ret = 0;

   reps(i, 1, alen){
      reps(j, 1, blen){
         if(a[i] == b[j]){
            dp[i][j] = dp[i-1][j-1] + 1;
         } else {
            dp[i][j] = max(dp[i-1][j] , dp[i][j-1] );
         }
         chmax(ret, dp[i][j]);
      }
   }
   return(ret);
}

signed main()
{
   FAST();
   int N;
   string a,b;
   cin >> N;
   rep(i, N){
      cin >> a >> b;
      outl( slv(a, b) );
   }
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i,o,n) for(long long i = o;i<n;i++)
#define oneforall ios::sync_with_stdio(false);cin.tie(0);
#define all(v) (v).begin(),(v).end()
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) long long __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define int long long 
const long long inf=1e18;
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
typedef vector<int> vi;
typedef vector<long long> vl;
typedef long long ll;
typedef vector<pair<long, long > > vpll;
typedef vector<pair<int, int > > vpii;
#define FORR(x,arr) for(auto& x:arr)
#define ZERO(a) memset(a,0,sizeof(a))





//3111111111111111111111111111111
	
	int dp[3100][3100];

	
	void solve(){

		ini(n);
		while (n--)
		{
			ins(morty);
			ins(morty1);
			FOR(i,0,morty.size()+1)
			FOR(i1,0,morty1.size()+1)
			dp[i][i1] = 0;

			FOR(i,0,morty.size()+1)
			FOR(i1,0,morty1.size()+1){
				if(morty[i] == morty1[i1]){
					dp[i+1][i1+1] = dp[i][i1]+1;
				}
				else{
					dp[i+1][i1+1] = max(dp[i][i1+1],dp[i+1][i1]);
				}
			}
			out(dp[morty.size()][morty1.size()]);
		}
		
		

		


		
		
	}























int32_t main() {
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall
	oneforall 
	oneforall

	solve();
	


	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>

using namespace std;

#define MAX_LEN 1000

int dp[MAX_LEN + 1][MAX_LEN + 1];

int main() {
	int q;
	cin >> q;
	while (q-->0) {
		string X, Y;
		cin >> X >> Y;
		for (int i = 0; i <= X.size(); ++i)
			for (int j = 0; j <= Y.size(); ++j)
				dp[i][j] = 0;
		for (int i = 0; i < X.size(); ++i)
			for (int j = 0; j < Y.size(); ++j)
				if (X[i] == Y[j])
					dp[i+1][j+1] = dp[i][j] + 1;
				else
					dp[i+1][j+1] = max(dp[i][j + 1], dp[i + 1][j]);
		cout << dp[X.size()][Y.size()] << endl;
	}
	return 0;
}

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

int main(){
    int q;
    cin >> q;
    for(int i = 0; i < q; i++){
        string x, y;
        cin >> x >> y;
        vector<vector<int>> dp(x.size()+1, vector<int>(y.size()+1, 0));
        
        for(int j = 1; j <= x.size(); j++){
            for(int k = 1; k <= y.size(); k++){
                if(x[j-1] == y[k-1]) dp[j][k] = dp[j-1][k-1]+1;
                dp[j][k] = max(dp[j][k], max(dp[j-1][k], dp[j][k-1]));
            }
        }

        cout << dp[x.size()][y.size()] << endl;
    }   
}

C++: #include<iostream>
#include<algorithm>
#include<string>

using namespace std;

int lcs (string x, string y) {

    int m, n, c[1001][1001], i, j, maxl = 0;

    m = x.size();
    n = y.size();

    x = ' ' + x;
    Y = ' ' + y;

    for (i = 0; i <= m; i++) {
        c[i][0] = 0;
    }
    for (j = 1; j <= n; j++) {
        c[0][j] = 0;
    }

    for (i = 1; i <= m; i++) {
            for (j = 1; j <= n; j++) {

                if (x[i - 1] == y[j - 1]) {
                    c[i][j] = c[i - 1][j - 1] + 1;
                } else {
                    c[i][j] = max (c[i - 1][j], c[i][j - 1]);
                }

                maxl = max (max, c[i][j]);

            }
    }

    return maxl;

}



int main () {

    int N, i;
    string x, y;

    cin >> N;

    for (i = 0; i < n; i++) {
        cin >> x >> y;
        cout << lcs (x, y) << endl;

    }

    return 0;

}

C++: #include "bits/stdc++.h"

using namespace std;

// https://onlinejudge.u-aizu.ac.jp/courses/lesson/1/ALDS1/all/ALDS1_10_C

int lcs(int currX, int currY, const string& X, const string& Y, vector<vector<int>>& memo) {
    if (currX == X.size() || currY == Y.size()) {
        return 0;
    }
    if (memo[currX][currY] >= 0) {
        return memo[currX][currY];
    }

    int ret;
    if (X[currX] == Y[currY]) {
        ret = lcs(currX + 1, currY + 1, X, Y, memo) + 1;
    }
    else {
        int moveX = lcs(currX + 1, currY, X, Y, memo);
        int moveY = lcs(currX, currY + 1, X, Y, memo);
        ret = max(moveX, moveY);
    }
    memo[currX][currY] = ret;
    return ret;
}

void Main() {
    int q;
    cin >> q;
    for (int i = 0; i < q; ++i) {
        string X, Y;
        cin >> X;
        cin >> Y;

        vector<vector<int>> memo(1005, vector<int>(1005, -1));
        int ans = lcs(0, 0, X, Y, memo);
        cout << ans << endl;
    }
}

int main() {
    std::cout << std::fixed << std::setprecision(15);
    Main();
    return 0;
}