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>
#define _GLIBCXX_DEBUG
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep1(i, n) for (int i = 1; i < (n); ++i)
using namespace std;
typedef long long ll;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int q;
    cin >> q;
    vector<int> res(q);

    rep(_, q){
        string x, y;
        cin >> x >> y;
        if(y.size() > x.size()) swap(x, y);

        int n = y.size();
        int m = x.size();

        vector<vector<int>> dp(n, vector<int>(m, 0));
        if(x[0] == y[0]) dp[0][0] = 1;
        else dp[0][0] = 0;

        rep1(i, m){
            if(y[0] == x[i]) dp[0][i] = 1;
            else dp[0][i] = dp[0][i-1];
        }

        rep1(i, n){
            dp[i][0] = dp[i-1][0];
            if(y[i] == x[0]) dp[i][0] = 1;

            rep1(j, m){
                if(y[i] == x[j]) dp[i][j] = dp[i-1][j-1] + 1;
                else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
            }
        }

        // rep(i, n){
        //     rep(j, m) cout << dp[i][j] << " ";
        //     cout << endl;
        // }

        cout << dp[n-1][m-1] << endl;
        
    }

    return 0;
}

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

using namespace std;
#define rep(i, n) for (ll i = 0; i < (n); ++i)
//#define rep(i, n) for (int i = 0; i < (n); ++i)
#define sz(x) ll(x.size())
//typedef long long ll;
typedef long long ll;
//typedef pair<int, int> P;
//typedef pair<ll, ll> P;
//const double INF = 1e10;
const ll INF = 10e15;
const ll MINF = -10e10;
//const int INF = INT_MAX / 100;
#define cmin(x, y) x = min(x, y)
#define cmax(x, y) x = max(x, y)


//ifstream myfile("~/Downloads/02.txt");
//ofstream outfile("log.txt");
//outfile << setw(6) << setfill('0') << prefecture << setw(6) << setfill('0') << rank << endl;
// std::cout << std::bitset<8>(9);

//typedef priority_queue<P, vector<P>, greater<P> > PQ_ASK;
const int mod = 1000000007;
const double PI = 3.14159265358979323846;

typedef pair<ll, ll> P;


string to_upper(string str) {
    int diff = 'a' - 'A';
    for (int i = 0; i < str.size(); i++) {
        char c = str[i];
        if ('A' <= c && c <= 'Z') {
            c += diff;
            str[i] = c;
        }
    }
    return str;
}


int main() {

    int n;
    cin >> n;

    rep(k, n) {

        string s1, s2;
        cin >> s1 >> s2;
        vector<vector<pair<int, pair<int, int> > > > dp(s1.size() + 1,
                                                        vector<pair<int, pair<int, int> > >(s2.size() + 1));
        for (int i = 0; i <= s1.size(); i++) {
            for (int j = 0; j <= s2.size(); j++) {
                if (i == 0 || j == 0) {
                    dp[i][j] = make_pair(0, make_pair(-1, -1));
                } else {
                    dp[i][j] = dp[i][j - 1];
                    if (dp[i][j].first < dp[i - 1][j].first) {
                        dp[i][j] = dp[i - 1][j];
                    }
                    if (s1[i - 1] == s2[j - 1] && dp[i][j].first < dp[i - 1][j - 1].first + 1) {
                        dp[i][j] = make_pair(dp[i - 1][j - 1].first + 1, make_pair(i - 1, j - 1));
                    }
                }
            }
        }
        vector<char> subseq_stack;
        for (int i = s1.size(), j = s2.size(); i > 0 && j > 0;) {
            pair<int, int> next = dp[i][j].second;
            //make_pair(i,j) = next;
            i = next.first;
            j = next.second;
            if (i < 0 || j < 0) break;
            subseq_stack.push_back(s1[i]); // s1[i] == s2[j]
        }
        cout << subseq_stack.size() << endl;
    }
}

C++: #include<iostream>
#include<algorithm>
#include<cstdio>
#include<string>
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 ;
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxx = 1010;
int c[maxx][maxx];

int lcs(char s1[],char s2[]) {
	int m = strlen(s1), n = strlen(s2);
	for (int i = 1; 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 (s1[i] == s2[j])
				c[i][j] = c[i - 1][j - 1] + 1;
			else
				c[i][j] = max(c[i - 1][j], c[i][j - 1]);
		}
	}
	return c[m][n];
}
int main()
{
	char s1[maxx], s2[maxx];
	int t;
	scanf("%d", &t);
	getchar();
	for (int i = 0; i < t; i++) {
		scanf("%s %s", s1, s2);
		printf("%d\n", lcs(s1,s2));
	}

	return 0;
}