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++: // 最長共通部分列 問題
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<stack>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<vector>

using namespace std;

#define MAX_LEN 1000
// 無効な値の定義
const int INV = -1;

int longestCommonSubstring(string a, string b);

int main(void)
{

    int q, len;
    string first_str, second_str;

    cin >> q;

    for(int i = 0; i < q; i++)
    {
        cin >> first_str;
        cin >> second_str;

        len = longestCommonSubstring(first_str, second_str);
        printf("%d\n", len);
    }



    return 0;
}

// 最長共通部分列を算出する関数
int longestCommonSubstring(string str_a, string str_b)

{
    int dp[MAX_LEN + 1][MAX_LEN + 1];
    int a_len, b_len;

    a_len = str_a.size();
    b_len = str_b.size();

    // 文字列の先頭に空白を挿入する
    str_a = " " + str_a;
    str_b = " " + str_b;

    for(int i = 0; i <= a_len; i++)
    {
        dp[i][0] = 0;
    }

    for(int j = 0; j <= b_len; j++)
    {
        dp[0][j] = 0;
    }

    // 最長共通部分列の算出
    for(int i = 1; i <= a_len; i++)
    {
        for(int j = 1; j <= b_len; j++)
        {
            if( str_a[i] == str_b[j] )
            {
                // 最後の文字が一致している時
                dp[i][j] = dp[i - 1][j - 1] + 1;
            }
            else
            {
                // 最後の文字が一致していない時
                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
            }
        }
    }

	return dp[a_len][b_len];
}

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

using namespace std;

void
chmax(int& aa, int bb)
{
  if (aa < bb) {
    aa = bb;
  }
}

int
main()
{
  int   qq;

  cin >> qq;

  
  for (int qi = 0; qi < qq; qi++) {
    string      xx;
    string      yy;
    vector<vector<int> > dp;

    cin >> xx;
    cin >> yy;

//    cout << xx << endl;
//    cout << xx.length() << endl;

    dp.assign(xx.length() + 1, vector<int>(yy.length() + 1, 0));

    for (int xi = 0; xi < xx.length(); ++xi) {
      for (int yi = 0; yi < yy.length(); ++yi) {
        //cout << yi << endl;
        if (xx[xi] == yy[yi]) {
          dp[xi + 1][yi + 1] = dp[xi][yi] + 1;
        }
        chmax(dp[xi + 1][yi + 1], dp[xi][yi + 1]);
        chmax(dp[xi + 1][yi + 1], dp[xi + 1][yi]);
      }
    }
    cout << dp.back().back() << endl;
  }
}

C++: #include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<vector>
#include<stdio.h>
#include<cstring>
#include<math.h>
#include<map>
#include<bitset>
#include<iomanip>
#include<queue>
#include<functional>
#include<stack>
#include<tuple>
#include<cassert>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
using P = pair<int, int>;

int n;
int dp[1001][1001];

int main() {
  cin >> n;
  rep(i, n) {
    string x, y;
    cin >> x >> y;
    dp[0][0] = 0;
    rep(i, y.size()) {
      dp[0][i+1] = 0;
    }
    rep(i, y.size()) {
      dp[i+1][0] = 0;
    }
    rep(i, x.size()) {
      rep(j, y.size()) {
        dp[i+1][j+1] = max(dp[i][j+1], dp[i+1][j]);
        if(x[i] == y[j]) {
          dp[i+1][j+1] = dp[i][j] + 1;
        }
      }
    }
    cout << dp[x.size()][y.size()] << endl;
  }


  return 0;
}

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

using namespace std;

int lcs(string x,string y){
    int m = x.size();
    int n = y.size();
    int lcs_lst[m+1][n+1];
    x = ' '+x;
    y = ' '+y;
    for(int i=0;i<=m;i++) lcs_lst[i][0] = 0;
    for(int i=1;i<=n;i++) lcs_lst[0][i] = 0;

    int ans = 0;
    for(int i=1;i<=m;i++){
        for(int j=1;j<=n;j++){
            if(x[i] == y[j])
                lcs_lst[i][j] = lcs_lst[i-1][j-1]+1;
            else{
                lcs_lst[i][j] = max(lcs_lst[i][j-1],lcs_lst[i-1][j]);
            }
            ans = max(ans,lcs_lst[i][j]);

        }
    }

    return ans;
}

int main(){
    int n; cin >> n;
    string a,b;
    for(int i=0;i<n;i++){
        cin >> a >> b;
        cout << lcs(a,b) << endl;
    }
}