Go: package main

import (
	"fmt"
	"os"
	"strconv"
	"bufio"
	"strings"
	"sort"
)

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// if S[i-1] == T[j-1] {
				// 	dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				// } else {
				// 	dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				// }
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

C++: #include <stdio.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <math.h>
#include <string>
#include <string.h>

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)

using namespace std;
int dp[1001][1001];
//?????????????????????
int n;
string x,y;
void solve(){
	cin >> n;
	REP(j,n){
	cin >> x >> y;
	memset(dp,0,1001*1001);
	int xn = x.size();
	int yn = y.size();
	REP(jj,xn+1){
		 REP(ii,yn+1){
			 if(jj <= 0 || ii <= 0){
				 dp[jj][ii] = 0 ;
			 }
			 else if(x[jj-1]==y[ii-1]) {
				 dp[jj][ii] = 1 + dp[jj-1][ii-1];
			 }
			 else{
				 dp[jj][ii] = max ( dp[jj-1][ii], dp[jj][ii-1] );
		   }
			 //cout << '('<<ii<<','<<jj<<')'<<dp[jj][ii]<<endl;
		 }

	}
	cout << dp[xn][yn]<<endl;
	}


}


int main(){
solve();
}

C++: #include <iostream>

using namespace std;

int lcs(string X, string Y) {
  int memo[1010][1010];
  int maxl = 0;

  for (int i = 0; i < X.size(); i++) {
    for (int j = 0; j < Y.size(); j++) {
      if (X[i] == Y[j]) {
        if (i == 0 || j == 0) {
          memo[i][j] = 1;
        } else {
          memo[i][j] = memo[i-1][j-1] + 1;
        }
      } else {
        if (i == 0 || j == 0) {
          memo[i][j] = 0;
        } else {
          memo[i][j] = max(memo[i-1][j], memo[i][j-1]);
        }
      }
      maxl = max(maxl, memo[i][j]);
      //cout << i << "," << j << "," << X[i] << "," << Y[j] << "," << maxl << endl;
    }
  }
  return maxl;
}

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

C++: #define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
//#include "MyMath.h"
//#include "DataStructure.h"
#include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <functional>
#include <stdio.h>
using namespace std;
typedef pair<int, int> p;
const int INF = 1000000000;
int main(){
	int n; cin >> n;
	for (int k = 0; k < n; k++) {
		char s[1000], t[1000];
		scanf("%s",&s); scanf("%s", &t);
		int i = 0, j = 0;
		int dp[1001][1001];
		fill(dp[0], dp[1001], 0);
		int res = 0;
		while (s[i] != '\0'){
			while (t[j] != '\0') 
			{
				if (s[i] == t[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]);
				res = dp[i + 1][j + 1];
				//cout << "i " << i << "j " << j << endl;
				//cout << "dp" << dp[i + 1][j + 1] << endl;
				j++;
			}
			i++;
			j = 0;
		}

		cout << res << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <string>
using namespace std;
int main(){

    string a,b;
    int n,nmax;
    
    cin>>n;
    for(int i=0;i<n;i++){
        int dp[1000]={0},result=0;
        cin>>a>>b;
        for(int j=0;j<a.size();j++) if(b[0]==a[j]) dp[j]++;
        for(int j=1;j<b.size();j++){
            nmax=0;
            if(b[j]==a[0]) dp[0]=1;
            for(int k=1;k<a.size();k++){
                nmax=max(dp[k-1],nmax);
                if(b[j]==a[k]) dp[k]=nmax+1;
            }
        }
        nmax=0;
        for(int j=0;j<a.size();j++) nmax=max(dp[j],nmax);
        cout<<nmax<<endl;
        
    }
    
    return 0;
    
}

C++: #include <iostream> 
#include <cstring> 
using namespace std;
int c[1001][1001];

int lcs(string x, string y)
{
    int maxl = 0;
    for (int i = 0; i < x.size(); i++)
    {
        c[i][0] = 0;
    } 
    for (int i = 0; i < y.size(); i++)
    {
        c[0][i] = 0; 
    }
    for (int i = 1; i <= x.size(); i++)
    {
        for (int j = 1; j <= y.size(); j++)
        {
            if (x[i]==y[j])
            { 
                c[i][j] = c[i][j-1] + 1; 
            }else
            {
                c[i][j] = max(c[i][j-1], c[i-1][j]);
            }
            maxl = max(maxl, c[i][j]);
        } 
    } 
    return maxl;
}

int main()
{
    string x,y;
    int q;
    cin>>q;
    while(q--)
    {
        cin>>x>>y;
        int ans = lcs(x, y);
        cout<<ans<<endl;
    }
    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 = 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;
}