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 <bits/stdc++.h>
using namespace std;

static const int N = 1000;

int lcs(string X,string Y){
    int c[N+1][N+1];    //c[i][k]???Xi??¨Yk???LCS??¨??????????????????
    int m = X.size();
    int n = Y.size();
    int maxl = 0;
    X = ' ' + X; // X[0]?????????????????\
    Y = ' ' + Y;
    for(int i=1;i<=m;i++) c[i][0] = 0;
    for(int k=1;k<=n;k++) c[0][k] = 0;

    for(int i=1;i<=m;i++){
        for(int k=1;k<=m;k++){
            if(X[i]==Y[k]){
                c[i][k] = c[i-1][k-1] + 1;
            } else {
                c[i][k] = max(c[i-1][k],c[i][k-1]);
            }
            maxl = max(maxl,c[i][k]);
        }
    }

    return maxl;
}

int main(){
    string s1,s2;
    int n;scanf("%d",&n);
    for(int i=0;i<n;i++){
        cin >> s1 >> s2;
        printf("%d\n",lcs(s1,s2));
    }

    return 0;
}

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

int a[1001][1001] = {0};

int main(){
	int n;
	cin >> n;
	string x;
	string y;
	for ( int i = 0; i < n; i++ ) {
		cin >> x;
		cin >> y;
		for ( int j = 0; j < x.size(); j++ ) {
			int f = 0;
			for ( int k = 0; k < y.size(); k++ ) {
				if ( x[j] == y[k] ) {
					a[j+1][k+1] = a[j][k] + 1;
				}else {
					a[j+1][k+1] = max(a[j+1][k],a[j][k+1]);
				}
				cout << a[j+1][k+1];
			}
			cout << endl;
		}
		cout << a[x.size()][y.size()] << 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 = 0; 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<string>
using namespace std;

int lcs(string X, string Y) {
  int m = X.size();
  int n = Y.size();
  int c[m+1][n+1];
  X = ' ' + X;
  Y = ' ' + Y;
  for (int i=0; i<m+1; i++) {
    c[i][0] = 0;
  }
  for (int j=0; j<n+1; j++) {
    c[0][j] = 0;
  }

  int max_lcs = 0;
  for (int i=1; i<m+1; i++) {
    for (int j=1; j<n+1; 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]);
      }
      max_lcs = max(max_lcs, c[i][j]);
    }
  }

  return max_lcs;
}


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

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

#define _For(idx, from, to, inc, cmp) \
	for(auto idx=(from) ; idx cmp (to) ; inc idx)
#define ForLE(idx, from, to) \
	_For(idx, from, to, ++, <=)
#define For(idx, from, to) \
	_For(idx, from, to, ++, <)

constexpr int MaxLen = 1000;
int Memo[MaxLen+1][MaxLen+1];
int main() {
	std::string line;
	const auto nextline = [&line](){
		std::getline(std::cin, line);
	};
	nextline();
	const int NQ = std::stoi(line);
	For(i, 0, NQ) {
		std::string s0, s1;
		std::getline(std::cin, s0);
		std::getline(std::cin, s1);

		int len0 = s0.length(),
			len1 = s1.length();
		if(len0 < len1) {
			std::swap(s0, s1);
			std::swap(len0, len1);
		}
		ForLE(j, 0, len0)
			Memo[j][0] = 0;
		ForLE(j, 0, len1)
			Memo[0][j] = 0;

		ForLE(j, 1, len1) {
			ForLE(k, 1, len0) {
				int res = std::max(
								Memo[k][j-1],
								Memo[k-1][j]
							);
				if(s0[k-1] == s1[j-1])
					res = std::max(Memo[k-1][j-1] + 1, res);
				Memo[k][j] = res;
			}
		}
		std::cout << Memo[len0][len1] << std::endl;
	}
	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define fs first
#define sc second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
#define RALL(A) A.rbegin(),A.rend()
typedef long long ll;
typedef pair<ll,ll> P;
const ll mod=1000000007;
const ll LINF=1LL<<60;
const int INF=1<<30;

int main(){
	int q;cin>>q;
	for(int i = 0; i < q; i++) {
		string x,y;cin>>x>>y;
		vector<vector<int>> dp(1001,vector<int>(1001,0));
		for(int i = 0; i < x.size(); i++) {
			for(int j = 0; j < y.size(); j++) {
				if (x[i] == y[j]){
					dp[i + 1][j + 1] = max(dp[i][j] + 1,max(dp[i][j + 1],dp[i + 1][j]));
				}
				else{
					dp[i + 1][j + 1] = max(dp[i][j + 1],dp[i + 1][j]);
				}
			}
		}
		cout << dp[x.size()][y.size()] << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <array>
#include <map>
#include <iterator>
#include <algorithm>

#define X first
#define Y second

using namespace std;

int q;
vector<pair<string,string>> dataset;

int ans(pair<string, string> &data)
{
    array<array<int,1001>,1001> dp = {};
    for (unsigned int i=1; i<=data.X.length(); ++i) {
        for (unsigned int j=1; j<=data.Y.length(); ++j) {
            if (data.X[i-1] == data.Y[j-1]) dp[i][j] = max({dp[i-1][j-1] + 1, dp[i-1][j], dp[i][j-1]});
            else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
        }
    }
    return dp[data.X.length()][data.Y.length()];
}

int main(int argc, char **argv)
{
    cin >> q;
    for (int i=0; i<q; ++i) {
        dataset.emplace_back(std::make_pair("",""));
        cin >> dataset[i].X;
        cin >> dataset[i].Y;
    }
    for (int i=0; i<q; ++i) {
        cout << ans(dataset[i]) << endl;
    }

    return 0;
}