Go: package main

import (
	"bufio"
	"os"
	"strconv"
	"fmt"
)

func max(x, y int) int {
	if x < y {
		return y
	} else {
		return x
	}
}

/*********************************************************************
長さmの列X_(m)と長さnの列Y_(n)の最長共通部分列LCSは、
	(1)X[m] == Y[n]ならば、X_(m-1)とY_(n-1)のLCSにX[m]を繋げたもの
	(2)X[m] != Y[n]ならば、X_(m-1)とY_(n)のLCSもしくはX_(m)とY_(n-1)のLCS
	のいずれかのうち長い方

c[m+1][n+1]：c[i][j]にX_(i)とY_(j)のLCSの長さを格納する二次元配列
*********************************************************************/

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	n, _ := strconv.Atoi(scanner.Text())
	for i := 0; i < n; i++ {
		scanner.Scan()
		s1 := scanner.Text()
		scanner.Scan()
		s2 := scanner.Text()
		s1, s2 = " " + s1 , " " + s2
		c := make([][]int, len(s1))
		for i := range c {
			c[i] = make([]int, len(s2))
		}

		LCS := 0

		for i := 1; i < len(s1); i++ {
			for j := 1; j < len(s2); 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])
				}
				LCS = max(LCS, c[i][j])
			}
		}
		fmt.Println(LCS)
	}
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int dp[1001][1001];
string s,t;
int n,m,a,ans;
int main(){
  cin>>a;
  for(int b=0;b<a;b++){
    cin>>s>>t;
    for(int i=0;i<=1000;i++)
      for(int j=0;j<=1000;j++)
    dp[i][j]=0;
    m=s.size();
    n=t.size();
    ans=0;
    for(int i=1;i<=m;i++){
      for(int j=1;j<=n;j++){
    if(s[i-1]==t[j-1]){
      dp[i][j]=dp[i-1][j-1]+1;
    }else{
      dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
    }
      }
    } 
    cout<<dp[m][n]<<endl;
  }
  return 0;
}

C++: #include<iostream>
#include<string>
#define N 1000

int c[N + 1][N + 1];

int max(int x, int y)
{
	return (x > y) ? x : y;
}

int lcs(std::string X, std::string Y)
{
	int ret = 0;
	int m = X.length();
	int n = Y.length();
	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][j - 1], c[i - 1][j]);
			}
			ret = max(c[i][j], ret);
		}
	}

	return ret;
}

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

	for (int i = 0; i < n; i++)
	{
		std::string x, y;
		std::cin >> x;
		std::cin >> y;
		std::cout << lcs(x, y) << std::endl;
	}
}

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

using namespace std;

typedef long long ll;

const ll LongINF=1e13+7;
const int INF=1e9+7;
const int dx[]={0,1,0,-1};
const int dy[]={1,0,-1,0};

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;}
template <class T, class Y>T GCD(T a, Y b){if(a<b){int c=a;a=b;b=c;}if (a % b == 0){return b;}return GCD(b, a % b);}
void clear(queue<pair<int, int>> &q){queue<pair<int, int>> empty;swap(q, empty);} //queueの中身の型は適時変更を忘れない

#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define rep(i,n) REP(i,0,n)
#define pb push_back
#define rv reverse

int main(){
    int N;
    cin>>N;
    rep(c,N){
        string A,B;
        cin>>A>>B;
        int a=A.length();
        int b=B.length();
        vector<vector<int> >dp(a+1,vector<int>(b+1,0));

        //i,j時点での最長文字列を格納する
        //一致した文字があればそこでインクリメントする。(iの時)
        //以前に共通文字列がカウントされていればそれに合わさる形となる。前後関係も正しい(i+1の時)

        rep(i,a){
            rep(j,b){
                if(A[i]==B[j])dp[i+1][j+1]=max(dp[i][j]+1,dp[i+1][j+1]);
                dp[i+1][j+1]=max(dp[i+1][j],dp[i+1][j+1]);
                dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j+1]);
            }
        }
        cout<<dp[a][b]<<endl;
    }

    return 0;
}

//a=97,z=122

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


int main(int argc, char *argv[]){
  int n;
  cin >> n;
  for (int r = 0; r < n; r++) {

    string x, y;
    cin >> x >> y;
    string dp[y.length() + 1][x.length() + 1];

    for (int i = 0; i < y.length(); i++) {
      for (int j = 0; j < x.length(); j++) {
        if(y[i] == x[j]){
          dp[i + 1][j + 1] = dp[i][j] + y[i];
        }else{
          dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
        }
      }
    }
    std::cout << dp[y.length()][x.length()].length() << std::endl;
  }
  return 0;
}