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<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<iostream>
using namespace std;

#define N_MAX 1000

char X[N_MAX];
char Y[N_MAX];
char LCS[N_MAX][N_MAX];


int longest(int x, int y)
{
    for (int i = 0; i < x+1; i++) {
        for (int j = 0; j < y+1; j++) {
            if (i == 0 || j == 0) {
                LCS[i][j] = 0;
//                printf("0 LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
            else if (X[i] == Y[j]) {
                LCS[i][j] = LCS[i-1][j-1] + 1;
//                printf("1 LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
            else {
                LCS[i][j] = (LCS[i-1][j] > LCS[i][j-1]) ? LCS[i-1][j] : LCS[i][j-1]; 
//                printf("LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
        }
    }

    return LCS[x][y]; 
}

int main() {
    int q;
    int x;
    int y;

    cin >> q;

    for (int i = 0; i < q; i++) {
        scanf("%s", X);
        x = strlen(X);
        scanf("%s", Y);
        y = strlen(Y);
        cout << longest(x, y) << endl;
    }
        
    return 0;
}

C++: // 最長共通部分裂問題

#include <bits/stdc++.h>

#define rep(i, a, n)  for(ll i=a; i<n; i++)
#define per(i, a, n)  for(ll i=n-1; i>=a; i--)
#define fill0(n)  setfill('0') << right << setw(n)
#define all(x)  (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define LONGMAX 1e18
#define INTMAX 1000000000

using namespace std;
typedef long long ll;
typedef pair<ll ,ll> P;
const ll mod = 1e9+7;
const long double EPS = 0.0000000001;


int n;
int main(){
	cin >> n;
	for(int a = 0; a < n; a++){
		string x,y;
		cin >> x;
		cin >> y;

		// dp start
		int W = x.size(); int H = y.size();
		int dp[H+1][W+1] = {0};
		for(int i = 0; i < H+1; i++){
			dp[i][0] = 0;
		}
		for(int i = 0; i < W+1; i++){
			dp[0][i] = 0;
		}
		for(int i = 1; i < H+1; i++){
			for(int j = 1; j < W+1; j++){
				if(x[j-1] == y[i-1]){
					dp[i][j] = max(max(dp[i-1][j-1] + 1, dp[i-1][j]), dp[i][j-1]);
				}else{
					dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
				}
			}
		}
		// cout << endl;
		// for(int i = 0; i < H+1; i++){
		// 	for(int j = 0; j < W+1; j++){
		// 		cout << dp[i][j] << " ";
		// 	}
		// 	cout << endl;
		// }

		cout << dp[H][W] << endl;
	}
}

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

using ll = long long;
using namespace std;

/* initialize */
int lcs(string A, string B){
    int m = A.length(), n = B.length();
    int c[m+1][n+1];
    int maxl = 0;
    A = ' ' + A;
    B = ' ' + B;
    for (int i = 0; i <= m; ++i) c[i][0]=0;
    for (int i = 1; i <= n; ++i) c[0][i]=0;
    for (int i = 1; i <= m; ++i) {
        for (int j = 1; j <= n; ++j) {
            if (A[i]==B[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;
};
/* main */
int main() {
    int n;
    cin >> n;
    string s1, s2;
    for (int i = 0; i < n; ++i) {
        cin >> s1 >> s2;
        int s = lcs(s1, s2);
        cout << s << "\n";
    }
    return 0;
}

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 = 0; 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]);
    }
  }

  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 <iostream>
#include <algorithm>
#include<string>
using namespace std;

static const int N = 1000;
static int dp[N + 1][N + 1];

int lcs(string x, string y)
{
    int m = x.length();
    int n = y.length();
    x = ' ' + x;
    y = ' ' + y;

    dp[0][0] = 0;
    for (int i = 1; i <= m; i++)
        dp[i][0] = 0;
    for (int j = 1; j <= n; j++)
        dp[0][j] = 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 <bits/stdc++.h>

using ll = long long;
using namespace std;
constexpr ll inf = 1e15;
constexpr ll mod = 1e9+7;

ll dp[1001][1001] = {0};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

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

        for (int i = 1; i <= X.length(); i++) {
            for (int j = 1; j <= Y.length(); j++) {
                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
                if (X[i-1] == Y[j-1]) dp[i][j] = max(dp[i][j], dp[i-1][j-1]+1);
            }
        }
        cout<<dp[X.length()][Y.length()]<<endl;
    }
    return 0;
}