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 <bits/stdc++.h>
using namespace std;

#define rep(i,x,y) for(int i=(x);i<(y);++i)
#define mp(a,b) make_pair((a),(b))
#define debug(x) #x << "=" << (x)
 
#ifdef DEBUG
#define _GLIBCXX_DEBUG
#define dump(x) std::cerr << debug(x) << " (L:" << __LINE__ << ")" << std::endl
#else
#define dump(x)
#endif

typedef long long int ll;
typedef pair<int,int> pii;
//template<typename T> using vec=std::vector<T>;

const int INF=1<<30;
const long long int INFLL=1LL<<58;
const double EPS=1e-9;
const int dx[]={1,0,-1,0},dy[]={0,1,0,-1};

template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec){
	os << "[";
	for (const auto &v : vec) {
		os << v << ",";
	}
	os << "]";
	return os;
}

void solve_(){
     string a,b;
    cin >> a >> b;
    
    static int dp[1000][1000];
    fill_n((int*)dp,1000*1000,0);
    
    rep(i,0,a.size()){
        rep(j,0,b.size()){
            if(i!=0) dp[i][j]=dp[i-1][j];
            if(j!=0) dp[i][j]=max(dp[i][j],dp[i][j-1]);
            
            if(a[i]!=b[j]) continue;
            
            if(i==0||j==0) dp[i][j]=1;
            else dp[i][j]=max(dp[i][j],dp[i-1][j-1]+1);
        }
    }
    
    cout << dp[a.size()-1][b.size()-1] << endl;
}

void solve(){
    int n;
    cin >> n;
    rep(i,0,n) solve_();
}

int main(){
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	solve();
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <string>
#include <list>
#include <stack>
#include <queue>
#include <algorithm>
#include <utility>
#include <vector>
#include <map>

using namespace std;

int main()
{
    int N;
    int data[1001][1001]={};
    cin>>N;
    string str1,str2;
    for(int i=0;i<N;i++){
        cin>>str1>>str2;
        for(int i=0;i<str1.length();i++){
            for(int j=0;j<str2.length();j++){
                if(str1[i]==str2[j]){
                    data[i+1][j+1]=data[i][j]+1;
                }else{
                    data[i+1][j+1]=data[i+1][j]>data[i][j+1]?data[i+1][j]:data[i][j+1];
                }
            }
        }
        cout<<data[str1.length()][str2.length()]<<endl;
    }
}

C++: /* 
*  入力された二つの文字列から最長共通部分列を求める。
*  二次元配列使用、動的計画法を利用する 
*/

#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]; // 二次元配列
	int m = X.size(); // 文字列１の長さ
	int n = Y.size(); // 文字列２の長さ
	int maxl = 0; // 文字列の最長の長さ
	X = ' ' + X; // X[0]に空白を挿入
	Y = ' ' + Y; // Y[0]に空白を挿入

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

	// 配列c[][]の中身確認
	/*for (int i = 0; i <= m; i++) {
		for (int j = 0; j <= n; j++) {
			cout << c[i][j] << ", ";
		}
		cout << endl;
	}*/

	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 <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <string>
#include <stack>
#include <vector>
#include <set>
#include <tuple>
#include <utility>
#include <functional>
using namespace std;
typedef long long ll;
typedef pair<int,int> P;

int main(){
	int q;
	cin >> q;
	vector<int> ans(q);
	for(int i = 0;i < q;i++){
		string s,t;
		cin >> s >> t;
		int n = s.size();
		int m = t.size();

		vector<vector<int>> dp(n+1,vector<int>(m+1,0));

		for(int i = 0;i < n;i++){
			for(int j = 0;j < m;j++){
				if(s[i] == t[j]){
					dp[i+1][j+1] = max({dp[i][j+1],dp[i+1][j],dp[i][j]+1});
				}
				else{
					dp[i+1][j+1] = max(dp[i+1][j],dp[i][j+1]);    
				}
			}
		}
		ans[i] = dp[n][m];
	}

	for(int a:ans)cout << a << endl;
}

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

using namespace std;

int solve(string s1, string s2){
    int L[s1.size()+1][s2.size()+1];
    for(int i=0;i<=s1.size();i++){
        for(int j=0;j<=s2.size();j++){
            if(i==0 || j==0){
                L[i][j]=0;
            }
            else if(s1[i] == s2[j]){
                L[i][j] = 1 + L[i-1][j-1];
            }
            else{
                L[i][j] = max(L[i][j-1],L[i-1][j]);
            }
        }
    }
    return L[s1.size()][s2.size()];
}

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