Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	Q := sc.nextInt()
	for q := 0; q < Q; q++ {
		X, Y := sc.nextStr(), sc.nextStr()
		xLen, yLen := len(X), len(Y)
		dp := make([][]int, xLen+1)
		for i := 0; i <= xLen; i++ {
			dp[i] = make([]int, yLen+1)
		}
		for x := 0; x <= xLen; x++ {
			for y := 0; y <= yLen; y++ {
				if x == 0 || y == 0 {
					dp[x][y] = 0
				} else if X[x-1] == Y[y-1] {
					dp[x][y] = dp[x-1][y-1] + 1
				} else {
					dp[x][y] = max(dp[x-1][y], dp[x][y-1])
				}
			}
		}
		fmt.Fprintln(wtr, dp[xLen][yLen])
	}

	wtr.Flush()
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
    int q;
    cin >> q;
    for(int qnum = 0; qnum < q; qnum++){
        string x, y;
        cin >> x;
        cin >> y;
        vector<vector<int>> memo(x.length()+1, vector<int>(y.length()+1, 0));
        for(int i = 0; i < x.length(); i++){
            for(int j = 0; j < y.length(); j++){
                if(x[i] == y[j]){
                    memo[i+1][j+1] = memo[i][j]+1;
                }else{
                    memo[i+1][j+1] = max(memo[i][j+1], memo[i+1][j]);
                }
            }
        }
        cout << memo[x.length()][y.length()] << endl;
    }
    return 0;
}

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

int main()
{
    int q;
    cin >> q;
    while (q > 0)
    {
        int dp[1010][1010] = {0};

        string X, Y;
        cin >> X >> Y;

        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] = max(dp[i + 1][j], dp[i][j] + 1);
                }
                dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
                dp[i][j + 1] = max(dp[i][j + 1], dp[i][j]);
            }
        }

        cout << dp[X.size()][Y.size()] << endl;
        q--;
    }
    return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
int main(void){
    int cnt;
    int n;
    std::cin>>n;

    for(int k=0;k<n;k++){
        std::string str1;
        std::string str2;
        std::cin>>str1;
        std::cin>>str2;
        int l1=str1.size();
        int l2=str2.size();
        int A[l1][l2]={};

        for(int i=0;i<l1;i++){
            for(int j=0;j<l2;j++){
                if(i==0 or j==0){
                    if(str1[i]==str2[j]){
                        A[i][j]=1;
                    }else if(i==0){
                        if(A[i][j-1]==1){
                            A[i][j]=1;
                        }
                    }else if(j==0){
                        if(A[i-1][j]==1){
                            A[i][j]=1;
                        }
                    }
                }else if(str1[i]==str2[j]){
                    A[i][j]=A[i-1][j-1]+1;
                }else{
                    A[i][j]=std::max(A[i][j-1],A[i-1][j]);
                }
                //std::cout<<A[i][j]<<" ";
            }
            //std::cout<<"\n";
        }
        std::cout<<A[l1-1][l2-1]<<"\n";
    }
    return 0;
}

C++: import java.util.*;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        String X = null, Y = null;
        int[][] dp = new int[1001][1001];

        int q = sc.nextInt();

        for (int i = 0; i < q; ++i) {
            X = sc.next();
            Y = sc.next();
            for (int x = 0; x < X.length(); ++x) {
                for (int y = 0; y < Y.length(); ++y) {
                    if (X.charAt(x) == Y.charAt(y)) {
                        dp[x + 1][y + 1] = dp[x][y] + 1;
                    }
                    else {
                        if (dp[x + 1][y] > dp[x][y + 1]) {
                            dp[x + 1][y + 1] = dp[x + 1][y];
                        }
                        else {
                            dp[x + 1][y + 1] = dp[x][y + 1];
                        }
                    }
                }
            }
            System.out.printf("%d\n", dp[X.length()][Y.length()]);
        }
    }
}

C++: #include <iostream>

using namespace std;

static const int N = 1000;

int lcs(string x, string y)
{
    int dp[N + 1][N + 1];
    int m = x.length();
    int n = y.length();
    x = ' ' + x;
    y = ' ' + y;

    for (int i = 1; i <= m; i++)
        dp[i][0] = 0;
    for (int i = 1; i <= n; i++)
        dp[0][i] = 0;

    int res = 0;
    for (int i = 1; i <= m; i++)
    {
        for (int j = 1; j <= n; j++)
        {
            if (x[i] == y[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[m][n];
}

int main()
{
    int n;
    cin >> n;
    string x1, x2;
    for (int i = 0; i < n; i++)
    {
        cin >> x1 >> x2;
        cout << lcs(x1, x2) << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<queue>
using namespace std;
int memo[1010][1010];
string x,y,q;
int lcs(int xn,int yn){//Y[yn]とX[xn]を比較
    if(memo[xn][yn]!=-1)return memo[xn][yn];
	else if(xn==0 || yn==0)return 0;
	else if(x[xn]==y[yn])return memo[xn][yn] = lcs(xn-1,yn-1)+1;
	else  return memo[xn][yn] = max(lcs(xn,yn-1),lcs(xn-1,yn));
}
 
 
int main(){
    int q;
    cin >> q;
    for(int ds=0; ds<q; ds++){
 
        cin >> x >> y;
        for(int i=0; i<=x.size(); i++){
            for(int j=0; j<=y.size(); j++)memo[i][j]=-1;
        }
        //memset(memo, -1, sizeof(memo));
         
        cout << lcs(x.size(),y.size()) << endl;
 
    }
    return 0;
}