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<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 = 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 <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i=0; i < (int)(n); i++)
using ull = unsigned long long;
using ll = long long;

int dp[1010][1010];

void LCS(string X, string Y) {
    rep(i, X.size()+1) rep(j, Y.size()+1) dp[i][j] = 0;

    rep(i, X.size()) rep(j, Y.size()) {
        if (X[i] == Y[j]) dp[i+1][j+1] = max({dp[i][j]+1, dp[i][j+1], dp[i+1][j]});
        else dp[i+1][j+1] = max({dp[i][j], dp[i][j+1], dp[i+1][j]});
    }

    cout << dp[X.size()][Y.size()] << endl;
}


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

    rep(i, q) {
        string x, y;
        cin >> x >> y;

        LCS(x, y);
    }

    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 i,j;
  int maxl=0;
  X=' '+X;
  Y=' '+Y;
 
  for(i=1;i<=m;i++) c[i][0]=0;
  for(j=1;j<=n;j++) c[0]c[j]=0;

  for(i=1;i<=m;i++){
    for(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)<<enl;
  }
  return 0;
}

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

int main(void){
	int q;
	string a,b;
	cin>>q;
	while(q--){
		cin>>a>>b;
		int dp[1010][1010] = {0};
		for(int j = 0 ; j < a.size() ; j ++){
			for(int i = 0 ; i < b.size() ; i ++){
				if(a[j] == b[i]){
					dp[j+1][i+1] = dp[j][i]+ 1;
				}else{
					dp[j+1][i+1] = max(dp[j][i+1],dp[j+1][i]);
				}
			}
		}
		cout<<dp[a.size()][b.size()]<<endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
#define all(x) (x).begin(),(x).end()
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; }
typedef long long ll;
const long long INF = 1LL << 60;
typedef pair<int, int> P;
int dp[1001][1001];
int main()
{
    int q;
    cin >> q;
    rep(i, q) {
        string A, B;
        cin >> A >> B;
        rep(i, A.size()) {
            rep(j, B.size()) {
                dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
                if (A[i] == B[j]) chmax(dp[i + 1][j + 1], dp[i][j] + 1);
            }
        }
        cout << dp[(int)A.size()][(int)B.size()] << endl;
    }
    return 0;
}

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

using namespace std;

int lcs(string a, string b)
{
	vector<vector<int> > dp(1001, vector<int>(1001));
	for (int i = 0; i < a.size(); ++i)
	{
		for (int j = 0; j < b.size(); ++j)
		{
			if (a[i] == b[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]);
			}
		}
	}
	return(dp[a.size()][b.size()]);
}

void solve()
{
	int q;
	cin >> q;
	for (int i = 0; i < q; ++i)
	{
		string a, b;
		cin >> a >> b;
		cout << lcs(a, b) << endl;
	}
}

int main()
{
	solve();
	return(0);
}

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

using namespace std;

int LCS(string X, string Y) {

	int lcs[X.size() + 1][Y.size() + 1];

	for (int i = 0; i < X.size(); ++i) {
		lcs[0][i] = 0;
	}
	for (int i = 0; i < Y.size(); ++i) {
		lcs[i][0] = 0;
	}

	for (int i = 1; i <= X.size(); ++i) {
		for (int j = 1; j <= Y.size(); ++j) {
			if (X[i - 1] == Y[j - 1]) {
				lcs[i][j] = lcs[i - 1][j - 1] + 1;
			} else if (lcs[i - 1][j] > lcs[i][j - 1]) {
				lcs[i][j] = lcs[i - 1][j];
			} else {
				lcs[i][j] = lcs[i][j - 1];
			}
		}
	}

	return lcs[X.size()][Y.size()];
}

int main() {

	int q;
	scanf("%d", &q);

	for (int i = 0; i < q; ++i) {
		string X, Y;
		cin >> X >> Y;
		cout << LCS(X, Y) << endl;
	}

	return 0;

}

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

using namespace std;


int solve(const string& s1, const string& s2) {
    const size_t N = 1000 + 1;
    int A[N][N] = {0};

    auto m = s1.size();
    auto n = s2.size();
    for (int i = 1; i <= m; ++i) {
        for (int j = 1; j <= n; ++j) {
            if (s1[i-1] == s2[j-1]) {
                A[i][j] = A[i-1][j-1] + 1;
            } else {
                A[i][j] = max(A[i][j-1], A[i-1][j]);
            }
        }
    }
    return A[m][n];
}

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

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

    return 0;
}