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 <cstdio>
#include <cstdlib>
#include <time.h>
#include <math.h>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <algorithm>
#include <iterator>
#include <sstream>
#include <string>
#include <bitset>
using namespace std;
#define FOR(I,F,N) for(int I = F; I < (int)(N); I++)
#define rep(i, n) FOR(i, 0, n)
#define FIN(V) cout<<V<<endl
#define pb push_back
#define INF (1 << 30)
typedef pair<int, int> P;
typedef long long ll;
typedef priority_queue<int> pq;
int StrToInt(string);
string IntToStr(int);
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};

int main(void){
	int q;
	cin >> q;
	rep(u, q){
		string S, L;
		cin >> S >> L;
		int dp[1002][1002];
		rep(i, S.size())
			rep(j, L.size()){
				if(S[i] == L[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]);
				}
			}
			FIN(dp[S.size()][L.size()]);
	}

	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include<string.h>
using namespace std;
int LCS(char *x,char *y);
char x[1001], y[1001];
int lcs[1001][1001];
int main()
{
	int q,i,j;

	cin >> q;
	for (i = 0; i < q; i++) {
		cin >> x;
		cin >> y;
		cout << LCS(x, y) << endl;
	}
}

int LCS(char *x, char *y)
{
	int i, j;
	int len_x, len_y;
	len_x = strlen(x);
	len_y = strlen(y);
	
	for (i = 0; i < len_x; i++) {
		if (x[0] == y[i]) {
			lcs[0][i] = 1;
		}
		else {
			lcs[0][i] = 0;
		}
	}
	for (i = 0; i < len_x; i++) {
		if (x[i] == y[0]) {
			lcs[i][0] = 1;
		}
		else {
			lcs[i][0] = 0;
		}
	}

	for (i = 0; i < len_x; i++) {
		for (j = 0; j < len_y; j++) {
			if (x[i] == y[j]) {
				lcs[i][j] = lcs[i - 1][j - 1] + 1;
				//printf("lcs[%d][%d]=%d\n", i, j, lcs[i - 1][j - 1] + 1);
			}
			if (x[i] != y[j]) {
				lcs[i][j] = max(lcs[i - 1][j], lcs[i][j - 1]);
				//printf("lcs[%d][%d]=%d\n", i, j, max(lcs[i - 1][j], lcs[i][j - 1]));
			}
		}
	}
	//cout << endl;

	for (i = 0; i < len_x; i++) {
		for (j = 0; j < len_y; j++) {
			//printf("%d ", lcs[i][j]);
		}
		//cout << endl;
	}
	//cout << "len_x=" << len_x << endl << "len_y=" << len_y << endl;
			
	return lcs[len_x-1][len_y-1];
}

C++: #define _USE_MATH_DEFINES
#define _CRT_SECURE_NO_WARNINGS

#include <iostream>
#include <string>
#include <sstream>
#include <iomanip>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <stack>
#include <queue>
#include <vector>
#include <list>
#include <utility>
#include <numeric>

using namespace std;
typedef long long llong;
typedef unsigned long long ullong;

const ullong MOD = 1000000000 + 7;

const int N = 1001;

int lcs(string x, string y)
{
	vector<vector<int>> c(N, vector<int>(N));

	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.at(i) == y.at(j))
			{
				c.at(i).at(j) = c.at(i - 1).at(j - 1) + 1;
			}
			else
			{
				c.at(i).at(j) = max(c.at(i).at(j - 1), c.at(i - 1).at(j));
			}

			maxl = max(maxl, c.at(i).at(j));
		}
	}

	return maxl;
}

int main()
{
	int n;
	for (cin >> n; n--;)
	{
		string s0, s1;
		cin >> s0 >> s1;

		cout << lcs(s0, s1) << endl;
	}
}

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

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

    for (int i = 0; i < n; i++)
    {
        string X, Y;
        cin >> X >> Y;
        vector<vector<int>> dp(X.size() + 1);
        for (int j = 0; j < dp.size(); j++)
        {
            dp[j].resize(Y.size() + 1, 0);
        }

        int res = 0;
        for (int j = 0; j < X.size(); j++)
        {
            for (int k = 0; k < Y.size(); k++)
            {
                if (X[j] == Y[k])
                {
                    dp[j + 1][k + 1] = dp[j][k] + 1;
                    res = max(res, dp[j + 1][k + 1]);
                }
                else
                {
                    dp[j + 1][k + 1] = max(dp[j][k + 1], dp[j + 1][k]);
                }

                // cout << "########## (" << j << ", " << k << ") ##########" << endl;
                // cout << dp[j + 1][k + 1] << endl;
            }
        }

        cout << res << endl;
    }

    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
int dp[1010][1010];
int main(){
  int q;
  cin>>q;
  for(int cn=0;cn<q;cn++){
    string x,y;
    cin>>x>>y;
    memset(dp,0,sizeof(dp));
    for(int i=1;i<=x.size();i++){
      for(int j=1;j<=y.size();j++){
	if(x[i-1]==y[j-1])dp[i][j]=dp[i-1][j-1]+1;
	dp[i][j]=max(dp[i-1][j],dp[i][j]);
	dp[i][j]=max(dp[i][j-1],dp[i][j]);
      }
    }
    cout<<dp[x.size()][y.size()]<<endl;
  }
  return 0;
}

C++: #include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<iostream>
using namespace std;
#define MAX 1000

int main(){
  int n;
  cin>>n;
  string a,b;
  for(int i=0;i<n;i++){
    cin>>a>>b;
    int C[MAX+1][MAX+1]={0};
    for(int i=1;i<=a.size();i++){
      for(int j=1;j<=b.size();j++){
        if(a[i-1]==b[j-1]) C[i][j]=C[i-1][j-1]+1;
        else{
          C[i][j]=max(C[i-1][j],C[i][j-1]);
        }
      }
    }
    cout<<C[a.size()][b.size()]<<endl;
  }

}

C++: #include <bits/stdc++.h>
using namespace std;
#define r(i,n) for(auto i=0;i<n;i++)
#define s(c) static_cast<int>((c).size())

int dp[1001][1001];
int main(){
	int n = 0;
	cin >> n;
	int x, y;
	string X, Y;
	r(k, n){
		cin >> X >> Y;
		x = X.length();
		y = Y.length();
		r(i, x+1)
			r(j, y+1)
				dp[i][j] = 0;

		r(i, x){
			r(j, y){
				if(X[i] == Y[j]){
					if(i == 0 || j == 0){
						dp[i][j] = 1;
					}else{
						dp[i][j] = dp[i-1][j-1] + 1;
					}
				}else{
					if(i == 0 || j == 0){
						dp[i][j] = 0;
					}else{
						dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
					}
				}

			}
		}
		cout << dp[x-1][y-1] << endl;
	}
	return 0;
}