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; //X[0]?????????????????\
    Y = ' ' + Y; //Y[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]);
        }
    }
    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 <vector>
#include <algorithm>

using namespace std;

const int MAXN = 1010;

int main(int argc, char const *argv[]) {
  int q;
  cin >> q;
  for (auto k = 0; k < q; k++) {
    vector<vector<int>> dp(MAXN, vector<int>(MAXN, 0));
    string s1, s2;
    cin >> s1 >> s2;
    auto n = s1.size();
    auto m = s2.size();
    for (size_t i = 0; i < n; i++) {
      for (size_t j = 0; j < m; j++) {
        if (s1[i] == s2[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;
  }

  return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int lcs(string s, string t) {
  int n = s.size(), 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++) {
      dp[i + 1][j + 1] =
          max(dp[i][j] + (s[i] == t[j]), max(dp[i][j + 1], dp[i + 1][j]));
    }
  return dp[n][m];
}

int main(void){
    int n;cin>>n;
    for(int i=0;i<n;i++){
        string s,t;cin>>s>>t;
        cout<<lcs(s,t)<<endl;
    }
    return 0;
}

C++: #include <cstdio>
#include <cstring>
#include <algorithm>

int count(int (*common)[1001], char *x, char *y, int n1, int n2){
    if(n1*n2==0)return 0;
    else if(common[n1][n2]<0){
        if(x[n1]==y[n2])common[n1][n2] = 1 + count(common,x,y,n1-1,n2-1);
        else common[n1][n2] = std::max(count(common,x,y,n1-1,n2),count(common,x,y,n1,n2-1));
    }
    return common[n1][n2];
}

int main(){
    int i, j, k, q;
    char c;
    char x[1002], y[1002];
    int common[1001][1001];
    scanf("%d",&q);
    for(i=0;i<q;i++){
        scanf("%s",x+1);
        scanf("%s",y+1);
        int n1 = strlen(x+1);
        int n2 = strlen(y+1);
        for(j=1;j<=n1;j++){
            for(k=1;k<=n2;k++){
                common[j][k] = -1;
            }
        }
        printf("%d\n",count(common,x,y,n1,n2));
    }
    return 0;
}

C++: #include <iostream>

using namespace std;

/**
 *  lcs(m,n) = 
 *  if x[m] == y[n] lcs[m-1,n-1]+1
 *  max(lcs[m-1,n],lcs[m,n-1])
 *
 */

string x, y;

int lcs(int m, int n)
{
	if (m == -1 || n== -1) return 0;
	if (x[m] == y[n]) return lcs(m-1,n-1) + 1;
	int xx = lcs(m-1,n);
	int yy = lcs(m,n-1);
	return xx > yy ? xx : yy;
}

int main()
{
	int n = 0;
	x.resize(150);
	y.resize(150);
	cin >> n; 
	for (int i=0;i<n;i++)
	{
		cin >> x;
		cin >> y;
		cout << lcs(x.size()-1, y.size()-1) << endl;
		x.clear();
		y.clear();
	}
}

C++: #include<iostream>
#include<algorithm>
#include<string>
using namespace std;
int main()
{
	int n, m, q, A[1001][1001], i, j;
	string str1, str2;
	cin >> q;

	while (q--)
	{
		cin >> str1 >> str2;
		n = str1.size();
		m = str2.size();
		int maxv = 0;

		for (i = 1; i <= n; i++)A[i][0] = 0;
		for (i = 1; i <= m; i++)A[0][i] = 0;

		for(i=1;i<=n;i++)
			for (j = 1; j <= m; j++)
			{
				if (str1[i-1] == str2[j-1])
					A[i][j] = A[i - 1][j - 1] + 1;
				else A[i][j] = max(A[i - 1][j], A[i][j - 1]);
			}
		cout << A[n][m] << endl;
	}
	return 0;
}

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

int lcs( string X , string Y) {
int c[ N + 1 ][ N + 1 ] ; 
int m = X.size() ; 
int n = Y.size() ; 
int max1 = 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]);
       }
       max1 = max(max1, c[i][j] ) ;
     }
   }
 return max1 ;
}

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 ;
}