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 <cstdlib>
#include <string>
#include <vector>
using namespace std;

int lcs_number(string a1, string a2){
	
	int n;
	if (a1.size() <= a2.size())
		n = a1.size() + 1;
	else
		n = a2.size() + 1;

	vector <vector <int> > A(n, vector <int> (n));

	for (int i1=0; i1<n; i1++)
		for (int i2=0; i2<n; i2++)
			if (i1==0 || i2==0)
				A[i1][i2] = 0;

			else if (a1[i1-1] == a2[i2-1])
				A[i1][i2] = A[i1-1][i2-1] + 1;

			else if (A[i1-1][i2] > A[i1][i2-1])
				A[i1][i2] = A[i1-1][i2];

			else
				A[i1][i2] = A[i1][i2-1];

			return A[n-1][n-1];
}

int main(void){
	int n;
	string text1, text2;
	cin>>n;

	for (int i=0; i<n; i++){
		cin>>text1;
		cin>>text2;
		cout<<lcs_number(text1, text2)<<endl;
	}

	return 0;
}

C++: #include<bits/stdc++.h>

using namespace std;


int main() {
    int q;
    cin >> q;

    vector<string> X(q), Y(q);
    int X_size, Y_size;

    vector<int> tmp(3, 0);

    for(int i = 0; i < q; i++) {
        cin >> X[i];
        cin >> Y[i];
    }

    for(int k = 0; k < q; k++) {
        X_size = X[k].size();
        Y_size = Y[k].size();

        // Xのi文字目までとTのj文字目までのLCSの長さdp[i][j]
        vector<vector<int> > dp(X_size+1, vector<int>(Y_size+1, 0));

        // 初期条件
        dp[1][0] = 0, dp[0][1] = 0;

        // dp開始
        for(int i = 1; i <= X_size; i++) {
            for(int j = 1; j <= Y_size; j++) {
                if(X[k][i-1] == Y[k][j-1]) {
                    tmp = {};
                    tmp.push_back(dp[i-1][j-1] + 1);
                    tmp.push_back(dp[i-1][j]);
                    tmp.push_back(dp[i][j-1]);
                    sort(tmp.begin(), tmp.end());
                    dp[i][j] = tmp.back();
                    // dp[i][j] = 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 << dp[X_size][Y_size] << endl;
    }

	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

using ll = long long;

// Longest Common Subsequence between X=x_1...x_m and Y=y_1...y_n
// O(mn)
// ALDS_1_10_C: verified
int main(){
    ll Q; cin >> Q;
    for(ll q=0;q<Q;q++){
        string X, Y; cin >> X >> Y;
        ll m = X.size(), n = Y.size();
        vector<vector<ll> > dp(m + 1, vector<ll>(n + 1));
        for(ll i=1;i<=m;i++){
            for(ll j=1;j<=n;j++){
                if(X[i-1] == Y[j-1]){
                    dp[i][j] = max(max(dp[i][j-1], dp[i-1][j]), dp[i-1][j-1] + 1);
                }else{
                    dp[i][j] = max(dp[i][j-1], dp[i-1][j]);
                }
            }
        }
        cout << dp[m][n] << endl;
    }
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <climits>
#include <string>
#include <vector>
#include <utility>
#include <functional>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <cassert>

using namespace std;

typedef long long ll;
typedef pair<int, int> P;

#define REP(i, n) for (ll i = 0; i < n; i++)
#define REPR(i, n) for (ll i = n; i >= 0; i--)
#define FOR(i, m, n) for (ll i = m; i < n; i++)

int dp[1001][1001];

int main() {
    int q;
    cin >> q;
    REP(i, q) {
        string s, t;
        cin >> s >> t;
        REP(i, s.size() + 1) REP(j, t.size() + 1) dp[i][j] = 0;
        REP(i, s.size()) {
            REP(j, t.size()) {
                if (s[i] == t[j])
                    dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + 1);
                dp[i + 1][j + 1] = dp[i + 1][j];
                dp[i + 1][j + 1] = dp[i][j + 1];
            }
        }
        cout << dp[s.size()][t.size()] << endl;
    }
    return 0;
}

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

using namespace std;

int lcs(string x,string y){
  int m=x.size();
  int n=y.size();
  int c[m+1][n+1];
  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(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]);
    }
  }
  return c[m][n];
}

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

C++: #include<stdio.h>

int strlen(char s[]) {
  int w = 0;
  while (1) {
    if (s[w] == '\0')
      break;
    w++;
  }
  return w;
}

int max(int a, int b, int c){
  int m = a;
  if (m < b)
    m = b;
  if (m < c)
    m = c;
  return m;
}

int main(void){
  int q, xl = 0, yl = 0, h = 0, i = 0, j = 0;
  int d, ans = 0;
  int DP[1001][1001];
  char X[1001], Y[1001];

  for (i = 0; i < 1001; i++) {
    DP[i][0] = 0;
  }
  for (i = 0; i < 1001; i++) {
    DP[0][i] = 0;
  }

  scanf("%d", &q);
  for (h = 0; h < q; h++) {

    scanf("%s", X);
    scanf("%s", Y);
    xl = strlen(X);
    yl = strlen(Y);

    for (i = 1; i <= xl; i++) {
       for (j = 1; j <= yl; j++) {
        if (X[i-1] == Y[j-1])
          d = 1;
        else
          d = 0;
        DP[i][j] = max(DP[i-1][j-1], DP[i-1][j], DP[i-1][j]) + d;
        if(DP[i][j] > ans)
          ans = DP[i][j];
      }
    }
    printf("%d\n", ans);
    ans = 0;
  }
  return 0;
}