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(){
	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] = 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<string>
#include<algorithm>
using namespace std;

int lcs(string x, string y){
    int n = x.size();
    int m = y.size();
    int dp[n+1][m+1];
    for(int i = 0;i<n+1;i++)dp[i][0] = 0;
    for(int j = 0;j<m+1;j++)dp[0][j] = 0;
    for(int i=0;i<n;i++){
        for(int j=0;j<m;j++){
            if(x[i]==y[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[n][m];
}

int main(){
    int n;cin>>n;
    // string s1,s2;
    for(int i=0;i<n;i++){
        string s1,s2;
        cin>>s1>>s2;
        cout<<lcs(s1,s2)<<endl;
    }
    return 0;
}

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

int main(){
	int q;
	std::string a, b;
	std::vector< std::vector< int > > dp;
	
	dp.resize(1001);
	for(int i=0;i<=1000;++i){
		dp[i].resize(1001);
	}
	
	std::cin >> q;
	
	for(int i=0;i<q;++i){
		std::cin >> a >> b;
		
		for(int x=1;x<=a.length();++x){
			for(int y=1;y<=b.length();++y){
				if(a[x-1] == b[y-1]){
					dp[x][y] = std::max(std::max(dp[x - 1][y - 1] + 1, dp[x][y - 1]), dp[x - 1][y]);
				}else{
					dp[x][y] = std::max(std::max(dp[x - 1][y - 1], dp[x][y - 1]), dp[x - 1][y]);
				}
			}
		}
		std::cout << dp[a.length()][b.length()] << std::endl;
	}
	
	return 0;
}

C++: #include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
#define rep(i,n) for(ll i=0;i<(n);i++)
#define repr(i,n) for(ll i=(n-1);i>=0;i--)
#define all(x) x.begin(),x.end()
#define br cout << "\n";
using namespace std;
const long long INF = 1e9;
const long long MOD = 1e9+7;
using Graph = vector<vector<ll>>;
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;}

// 0 false, 1 true 
// string to int : -48
// a to A : -32
// ceil(a)  1.2->2.0
// c++17	g++ -std=c++17 a.cpp

int main() {
    std::cout << std::fixed << std::setprecision(15);
    ll q; cin >> q;
    rep(Q, q){
        string s, t; cin >> s >> t;
        ll s_size = s.size(), t_size = t.size();

        vector<vector<ll>> dp(s_size+1, vector<ll>(t_size+1));

        for(ll i = 0; i < s_size; i++){
            for(ll j = 0; j < t_size; j++){
                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]);
                }
            }
        }

        cout << dp[s_size][t_size] << endl;

    }

}

C++: #include <iostream>
#include <cstring>
using namespace std;
char sz1[1000];
char sz2[1000];
int maxLen[1000][1000];
int main(){
int n;
cin>>n;
while( cin >> sz1 >> sz2 ){
int length1 = strlen( sz1);
int length2 = strlen( sz2);
int nTmp;
int i,j;
for( i = 0;i <= length1; i ++ )
maxLen[i][0] = 0;
for( j = 0;j <= length2; j ++ )
maxLen[0][j] = 0;
for( i = 1;i <= length1;i ++ ) {
for( j = 1; j <= length2; j ++ ){
if( sz1[i-1] == sz2[j-1] )
maxLen[i][j] = maxLen[i-1][j-1] + 1;
else
maxLen[i][j] = max(maxLen[i][j-1],maxLen[i-1][j]);
}
}
cout << maxLen[length1][length2] << endl;
n--;
if(n<1)break;
}
return 0;
}

C++: #include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <string>
#include <vector>

// Acknowledgement: Special thanks to kyomukyomupurin, who developed this
// template.
template <class T, class U>
std::ostream& operator<<(std::ostream& os, const std::pair<T, U>& p) {
  return os << '(' << p.first << ", " << p.second << ')';
}

template <class T>
std::ostream& operator<<(std::ostream& os, const std::vector<T>& vec) {
  int n = 0;
  for (auto e : vec) os << (n++ ? ", " : "{") << e;
  return os << (n ? "}" : "{}");
}

template <class T>
std::ostream& operator<<(std::ostream& os, const std::set<T>& st) {
  int n = 0;
  for (auto e : st) os << (n++ ? ", " : "{") << e;
  return os << (n ? "}" : "{}");
}

template <class T, class U>
std::ostream& operator<<(std::ostream& os, const std::map<T, U>& mp) {
  int n = 0;
  for (auto e : mp) os << (n++ ? ", " : "{") << e;
  return os << (n ? "}" : "{}");
}

template <class T>
std::istream& operator>>(std::istream& is, std::vector<T>& vec) {
  for (T& e : vec) is >> e;
  return is;
}

#ifdef LOCAL
#define debug(...) \
  std::cerr << "[" << #__VA_ARGS__ << "]: ", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out() { std::cerr << '\n'; }

template <class Head, class... Tail>
void debug_out(Head&& head, Tail&&... tail) {
  std::cerr << head;
  if (sizeof...(Tail) != 0) std::cerr << ", ";
  debug_out(std::forward<Tail>(tail)...);
}
using namespace std;
using int64 = long long;

int main() {
  int q;
  cin >> q;
  string X, Y;
  for (int _ = 0; _ < q; _++) {
    int mx = 0;
    cin >> X >> Y;
    X = ' ' + X;
    Y = ' ' + Y;
    int X_size = X.size();
    int Y_size = Y.size();
    vector<vector<int>> dp(X_size, vector<int>(Y_size));
    for (int i = 1; i < X_size; i++) {
      for (int j = 1; j < Y_size; j++) {
        if (X[i] == Y[j]) {
          dp[i][j] = dp[i - 1][j - 1] + 1;
        } else {
          dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
        mx = max(mx, dp[i][j]);
      }
    }
    cout << mx << endl;
  }
  return 0;
}