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

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, m, n) for (int i = m; i < n; ++i)
template<class T>bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }

int solve() {
  string X, Y;
  cin >> X >> Y;
  int N = X.size();
  int M = Y.size();
  int dp[1010][1010] = {};
  rep(i, 0, N) rep(j, 0, M) {
    if(X[i] == Y[j]) {
      chmax(dp[i + 1][j + 1], dp[i][j] + 1);
    } else {
      chmax(dp[i + 1][j + 1], dp[i + 1][j]);
      chmax(dp[i + 1][j + 1], dp[i][j + 1]);
    }
  }
  cout << dp[N][M] << "\n";
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int q; cin >> q;
  rep(i, 0, q) solve();
  return 0;
}

C++: import java.util.Scanner;

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>
#include<vector>
#include<string>
#include<algorithm>

using namespace std;

string s, t;

int main() {
	int n;
	cin >> n;
	while (n--) {
		//dp[i][j] := s???i??????????????§???t???j??????????????§?????£?????¨??????LCS
		vector<vector<int>> dp(2000, vector<int>(2000));
		cin >> s >> t;
		for (int i = 0; i < s.size(); i++) {
			for (int j = 0; j < t.size(); j++) {
				if (s[i] == t[j]) dp[i + 1][j + 1] = dp[i][j] + 1;
				else dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
			}
		}
		cout << dp[s.size()][t.size()] << endl;
	}
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
static const int N = 1000;

int lcs(string X, string Y) {
	int c[N + 1][N + 1];
	int m = X.size();
	int n = Y.size();
	int maxl = 0;
	X = ' ' + X;
	Y = ' ' + Y;
	for (int i = 1; i <= m; i++)c[i][0] = 0;
	for (int j = 0; j <= n; j++)c[0][j] = 0;

	for (int i = 1; i <= m; i++) {
		for (int j = 1; j <= n; j++) {
			if (X[i] == Y[j]) {
				c[i][j] = c[i - 1][j - 1] + 1;
			}
			else {
				c[i][j] = max(c[i - 1][j], c[i][j - 1]);
			}
			maxl = max(maxl, c[i][j]);
		}
	}

	return maxl;
}

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

	return 0;
}

C++: #include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < (n); ++i)
template <class T>
inline bool chmin(T &a, T b)
{
    if (a > b)
    {
        a = b;
        return true;
    }
    return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
    if (a < b)
    {
        a = b;
        return true;
    }
    return false;
}
using namespace std;
using ll = long long;
using P = pair<int, int>;
using Pl = pair<long long, long long>;
using veci = vector<int>;
using vecl = vector<long>;
using vecveci = vector<vector<int>>;
using vecvecl = vector<vector<long long>>;
#define INF 1e+9

vecveci dp(1010,veci(1010,0));

int main() {
    int Q; cin >> Q;
    while(Q--) {
        string S,T;
        cin >> S >> T;
        int n = S.size();
        int m = T.size();
        REP(i,n)REP(j,m) {
            if(S[i] == T[j]) dp[i+1][j+1] = dp[i][j] + 1;
            else dp[i+1][j+1] = max(dp[i+1][j],dp[i][j+1]);
        }
        cout << dp[n][m] << endl;
    }
}