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 <iostream>
#include <algorithm>
#include <utility>
#include <string>
#include <vector>
#include <set>
#include <stack>
#include <queue>
#include <map>
#include <math.h>
#include <string.h>
#include <iomanip>
#include <numeric>
#include <cstdlib>
#include <cstdint>
#include <cmath>
#include <functional>
#include <limits>

using namespace std;

using ll = long long;
using pll = pair<ll, ll>;
using vl = vector<ll>;
using vll = vector<vl>;
using vpll = vector<pll>;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rrep(i, n) for (int i = ((int)(n)-1); i >= 0; i--)
#define Rep(i, n) for (long long i = 0; i< (long long)(n); i++)
#define RRep(i,n) for (long long i = ((long long)(n)-1); i>=0; i--)
#define all(v) (v).begin(),(v).end()

struct Edge{
    int to;
    int weight;
    Edge(int t, int w) : to(t), weight(w){ }
};

struct edge{
    int from;
    int to;
    int weight;
    edge(int f,int t,int w) : from(f), to(t), weight(w){ }
};

using Graph = vector<vector<Edge>>;
using graph = vector<vector<int>>;
using edges = vector<edge>;

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;
}

template <class T>
T gcd(T a, T b){
    if( b==0 ) return a;
    return gcd(b, a%b);
}

template <class T>
T lcm(T a, T b){
    return (a*b)/gcd(a,b);
}

int INF = 1e9+7;

vector<int> dx = {-1,0,1,0};
vector<int> dy = {0,-1,0,1};

void solve(){
    string s,t;
    cin >> s >> t;
    int n = s.size();
    int m = t.size();
    vector<vector<int>> dp(n+1,vector<int>(m+1,0));
    rep(i,n) rep(j,m){
        if(s[i]==t[j]){
            dp[i+1][j+1] = max(dp[i][j]+1,max(dp[i+1][j],dp[i][j+1]));
        }
        else{
            dp[i+1][j+1] = max(dp[i][j+1],dp[i+1][j]);
        }
    }
    cout << dp[n][m] << endl;
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int t;
    cin >> t;
    rep(_,t) solve();
}

C++: #include<iostream>
#include<stdio.h>
#include<string.h>
#include<cstring>
using namespace std;

string lcs_f;
string lcs_s;
int maxnum = 0;

void lcs() {
    maxnum = 0;
	int flen = lcs_f.size() + 1;
	int slen = lcs_s.size() + 1;
	int a[1001][1001] ={};
	for (int i = 0; i < flen; i++) {
		for (int j = 0; j < slen; j++) {
			if (i == 0 || j == 0) {
				a[i][j] = 0;
			}
			else if (lcs_f[i-1] == lcs_s[j-1]) {
				a[i][j] = a[i - 1][j - 1] + 1;
				if (a[i][j] > maxnum) {
				    maxnum = a[i][j];
				}
			}
			else {
				if (a[i][j - 1] < a[i - 1][j]) {
					a[i][j] = a[i - 1][j];
				}
				else {
					a[i][j] = a[i][j-1];
				}
				 
			}
		}
	}
	
	
}

int main() {
	int n;
	
	cin >> n;
	for (int i = 0; i < n; i++){
		cin >> lcs_f >> lcs_s;
		lcs();
		cout << maxnum << endl;
	}
}

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

using namespace std;

int main() {
		
	long n;
	cin >> n ;

	for (long i = 0; i < n; i++) {
		string x, y;
		cin >> x >> y;
		long xl, yl;
		xl = x.size();
		yl = y.size();
		vector<vector<long>> dp(xl+1, vector<long> (yl+1,0));
		for (long j = 0; j < xl; j++) {
			for (long k = 0; k < yl; k++) {

				if (x[j] == y[k]) {
					dp[j+1][k+1] =dp[j][k]+1;
				}
				else{
					dp[j + 1][k + 1] = max(dp[j][k + 1], dp[j + 1][k]);
				}
			}
		}
		cout << dp[xl][yl] << endl;
	}

	return 0;

}

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

#define STR_MAX 1000

int mat[STR_MAX+1][STR_MAX+1];

int common_subsequence(int len1, int len2, string str1, string str2){
  int i, j;

  for(i=1; i<=len1; i++){
    for(j=1; j<=len2; j++){
      if(str1[i-1] == str2[j-1]) mat[i][j]=mat[i-1][j-1]+1;
      else mat[i][j]=max(mat[i-1][j], mat[i][j-1]);
    }
  }

  return mat[len1][len2];
}

int main(void){
  int i, n;
  string str1, str2;

  scanf("%d", &n);
  for(i=0; i<n; i++){
    cin >> str1 >> str2;

    int len1=str1.size(), len2=str2.size();
    printf("%d\n", common_subsequence(len1, len2, str1, str2));
  }
  
  return 0;
}

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

#define MAX 1000

int lcs(string X, string Y){
    int c[MAX + 1][MAX + 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 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] == 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<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++){
    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;
}