Go: package main

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

type Position struct {
	X int
	Y int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}
	for i := 0; i < n; i++ {
		strX := nextText(sc)
		strY := nextText(sc)
		fmt.Println(calcLcs(strX, strY))
	}
}

func calcLcs(strX, strY string) int {
	return lcs(strX, strY, Position{0, 0}, make(map[Position]int))
}

func lcs(strX string, strY string, position Position, memo map[Position]int) int {
	if position.X >= len(strX) || position.Y >= len(strY) {
		return 0
	}
	if v, ok := memo[position]; ok {
		return v
	}
	if strX[position.X] == strY[position.Y] {
		result := lcs(strX, strY, Position{position.X + 1, position.Y + 1}, memo)
		memo[position] = result + 1
		return memo[position]
	} else {
		result1 := lcs(strX, strY, Position{position.X + 1, position.Y}, memo)
		result2 := lcs(strX, strY, Position{position.X, position.Y + 1}, memo)
		var result int
		if result1 > result2 {
			result = result1
		} else {
			result = result2
		}
		memo[position] = result
		return result
	}
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: //
//  main.cpp
//  longest_common_subsequence
//
//  Created by ???????????? on 2017/10/17.
//  Copyright ?? 2017 ????????????. All rights reserved.
//

#include <iostream>
#include <stdio.h>
#include <string.h>

using namespace std;

char X[1005];
char Y[1005];

void lcs(){
    size_t m = strlen(X);
    size_t n = strlen(Y);
    int c[m+1][n+1];
    c[0][0] = 0;
    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 if(c[i-1][j] >= c[i][j-1]){
                c[i][j] = c[i-1][j];
            }
            else{
                c[i][j] = c[i][j-1];
            }
        }
    }
    cout << c[m][n] << endl;
//    cout << c[m+1][n+1] << endl;
}

int main(int argc, const char * argv[]) {
    int n, i;
    scanf("%d", &n);
    for (i = 0; i < n; i++){
        scanf("%s", X);
        scanf("%s", Y);
        lcs();
    }
//    std::cout << "Hello, World!\n";
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cstring>
#include <cctype>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <stdio.h>
#include <string.h>
#include <cstdlib>
#include <math.h>
#include <bitset>
#include <iterator>
#include <iomanip>
#include <sstream>
#define INF 2000000000
using namespace std;
int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
#define sym cout<<"---------"<<endl;
#define ll long long
#define PL pair<long long, long long>
#define P pair<int,int>
#define mk make_pair
#define en endl
#define WHITE 0
#define BLACK 2
#define GRAY 1
#define RE return 0
#define int ll

int dp[1005][1005];

signed main(){
  int n;
  cin>>n;
  for(int i=0; i<n; i++){
    string s1,s2;
    cin>>s1>>s2;
    s1=" "+s1;
    s2=" "+s2;
    for(int i=0; i<=s1.size(); i++) for(int j=0; j<=s2.size(); j++) dp[i][j]=0;
    for(int i=1; i<s1.size(); i++){
      for(int j=1; j<s2.size(); j++){
        if(s1[i]==s2[j]) dp[i][j]=dp[i-1][j-1]+1;
        else dp[i][j]=max(dp[i-1][j],dp[j-1][i]);
      }
    }
    cout<<dp[s1.size()-1][s2.size()-1]<<en;
  }
}

C++: #include <iostream>
#include <algorithm>
#include <climits>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
using namespace std;

int dp(int i, int j) {

}

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

    for (int k = 0; k <= Y.length(); ++k) {
        dp[0][k] = 0;
    }
    for (int k = 0; k <= X.length(); ++k) {
        dp[k][0] = 0;
    }

    for (int i = 1; i <= X.length(); ++i) {
        for (int j = 1; j <= Y.length(); ++j) {
            if (X[i] == Y[j]) {
                dp[i][j] = 1 + dp[i-1][j-1];
            } else{
                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
            }
        }
    }
    return dp[X.length()][Y.length()];
}
int main() {
    int N;
    cin >> N;
    for (int i = 0; i < N; ++i) {
        string X, Y;
        cin >> X >> Y;
        cout << solve(X, Y) << endl;
    }

    return 0;
}

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

bool isprime(int n){
    double rootn = sqrt(n);
    if (n < 2){
        return false;
    }
    else if (n == 2){
        return true;
    }
    else if (n % 2 == 0){
        return false;
    }
    else{
        for(int i = 3; i <= rootn; i += 2){
            if(n % i == 0){
                return false;
            }
        }
        return true;
    }
}

// 空のベクトルを二つ渡す。N (>=2) 以下の素数を primes に順番に入れる。
void prime_vectors(int N, vector<int>& primes, vector<bool>& is_prime){
    primes = {};
    is_prime = {};
    for(int i=0; i<=N; i++){
        is_prime.push_back(true);
    }

    primes.push_back(2);
    for(int j=4; j<=N; j+=2){
        is_prime[j] = false;
    }

    int i;
    for(i=3; i*i<=N; i+=2){
        if(!is_prime[i]) continue;
        primes.push_back(i);
        for(int j=2*i; j<=N; j+=i){
            is_prime[j] = false;
        }
    }

    for(; i<=N; i+=2){
        if(is_prime[i]){
            primes.push_back(i);
        }
    }
}

signed main(){
    // cout << fixed << setprecision(10) << flush;

    int q;
    cin >> q;
    vector<int> ans(q, 0);
    for(int ind=0; ind<q; ind++){
        string x, y;
        cin >> x >> y;
        // dp[i][j] は、x の i 文字目までの部分列のうち、y の j 文字目でちょうど終了するものの長さの最大
        // 最後には max_j dp[x.size()-1][j] を見れば ok
        vector<vector<int>> dp(x.size(), vector<int>(y.size(), 0));
        // i=0 だけ別処理
        for(int j=0; j<y.size(); j++){
            if(x[0] == y[j]) dp[0][j] = 1;
        }
        for(int i=1; i<x.size(); i++){
            int l = 0;
            for(int j=0; j<y.size(); j++){
                if(x[i] == y[j]){
                    dp[i][j] = max(dp[i-1][j], l+1);
                }
                else{
                    dp[i][j] = dp[i-1][j];
                }
                l = max(l, dp[i-1][j]);
            }
        }

        for(int j=0; j<y.size(); j++){
            ans[ind] = max(ans[ind], dp[x.size()-1][j]);
        }
    }

    for(int i=0; i<q; i++){
        cout << ans[i] << endl;
    }
    return 0;
}

C++: #include <bits/stdc++.h>
#include <iostream>
#include <string>
using namespace std;
int LCS(string A, string B)
{
    int s1 = A.size();
    int s2 = B.size();
    int X[s1 + 1][s2 + 2];
    for (int i = 0; i < s1+1; i++)
    {
        for (int j = 0; j < s2+1; j++)
        {
            if (i > 0 && j > 0)
            {
                if (A[i-1] == B[j-1])
                {
                    X[i][j] = max(X[i - 1][j - 1] + 1, max(X[i][j - 1], X[i - 1][j]));
                }
                else
                {
                    X[i][j] = max(X[i - 1][j], X[i][j - 1]);
                }
            }
            else
            {
                X[i][j] = 0;
            }
        }
    }
    int N = X[s1][s2];
    return N;
}
int main()
{
    int N;
    cin >> N;
    for(int i = 1; i < N + 1; i++){
        string A;
        string B;
        cin >> A;
        cin >> B;
        cout << LCS(A,B) << endl;
    }
    return 0;
}