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++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INF = 1e18;
const int inf = 1e9;
double pi = 3.14159265359;
#define rep(i, a, b) for (int i = a; i < b; i++)
#define per(i, b, a) for (int i = a - 1; i >= b; i--)
using Graph = vector<vector<int>>;
using pint = pair<int, int>;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
int dxx[8] = {1, 1, 1, 0, 0, -1, -1, -1}, dyy[8] = {-1, 0, 1, -1, 1, -1, 0, 1};

int main() {
    int q;
    cin >> q;
    rep (k, 0, q) {
        string s, t;
        cin >> s >> t;
        int sl = s.size(), tl = t.size();
        int dp[sl + 1][tl + 1];
        rep (i, 0, sl + 1) rep (j, 0, tl + 1) dp[i][j] = 0;
        rep (i, 0, sl) {
            rep (j, 0, tl) {
                if (s[i] == t[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], dp[i][j]});
            }
        }
        cout << dp[sl][tl] << "\n";
    }
}

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

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)

const int MAX_L=1001;//?????????????????§??????

vector<vector<int> > DP(MAX_L, vector<int>(MAX_L, -1));
string A;//?????????????????????????????????
string B;
string chars;//???????????????????????¨????????????????????????


//A???a???????????¨????????\??????B???b???????????¨????????\??????????????§????????§?????¨????????????????????????????????????
//m?????????????????????????????±??????????????????
int dev(int a, int b){
	if(DP[a][b]<0){
		int maxi= 0;
		//???????????????????????§??????
		for(char c: chars){
			int posa = A.find(c,a);
			int posb = B.find(c,b);
			if(posa>=0 && posb>=0){
				int tmp = dev(posa+1,posb+1);
				maxi = max(maxi, tmp+1);
			}
		}
		DP[a][b]=maxi;
	}
	return DP[a][b];
}

void make_list(){
		//???????????????????????§??????
		for(int c='a'; c<='z'; ++c){
			int posa = A.find(c,0);
			int posb = B.find(c,0);
			if(posa>=0&&posb>=0){
				chars.push_back(c);
			}
		}
		for(int c='A'; c<='Z'; ++c){
			int posa = A.find(c,0);
			int posb = B.find(c,0);
			if(posa>=0&&posb>=0){
				chars.push_back(c);
			}
		}
}

int main(){
	int q;
	cin >> q;
	vector<int> ans(q);
	REP(i,q){
		REP(k,MAX_L){
			REP(l,MAX_L){
				DP[k][l] = -1;
			}
		}
		chars="";
		cin>>A>>B;
		make_list();
		ans[i]=dev(0,0);
	}
	REP(i,q){
		cout<<ans[i]<<endl;
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <stack>
#include <vector>
#include <algorithm>
#include <cmath>
#include <climits>
#include <cstring>
#include <queue>
#include <string>

using namespace std;

const double PI = 3.14159265358979;

int dp[1001][1001];

void lcs(string x, string y) {

	for (int i = 0; i < x.length(); i++) {
		dp[i][0] = 0;
	}
	for (int i = 0; i < y.length(); i++) {
		dp[0][i] = 0;
	}

	for (int i = 1; i <= x.length(); i++) {
		for (int j = 1; j <= y.length(); j++) {

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


int main() {

	int n; cin >> n;

	for (int i = 0; i < n; i++)	{
		string big, small;
		cin >> big >> small;
		
		lcs(big, small);
		int res = dp[big.length()][small.length()];
		cout << res << endl;
	}
	

	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <set>
#include <queue>
#include <map>
#include <memory.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<ld> vld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define INF ((int)1e9)
#define INFLL ((ll)1e18)
#define MOD (1000000007LL)


int main(int argc, const char * argv[]) {
    int Q;
    string X, Y;
    cin >> Q;
    for (int q = 0; q < Q; ++q) {
        cin >> X >> Y;
        int DP[1001][1001];
        memset(DP, 0, sizeof(DP));
        for (int sx = 1; sx <= X.size(); ++sx) {
            for (int sy = 1; sy <= Y.size(); ++sy) {
                DP[sx][sy] = max(DP[sx-1][sy], DP[sx][sy-1]);
                if (X[sx-1] == Y[sy-1]) {
                    DP[sx][sy] = max(DP[sx][sy], DP[sx-1][sy-1]+1);
                }
            }
        }
        cout << DP[X.size()][Y.size()] << endl;
    }
    return 0;
}

C++: #include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<iostream>
using namespace std;

#define N_MAX 1000

char X[N_MAX];
char Y[N_MAX];
char LCS[N_MAX][N_MAX];


int longest(int x, int y)
{
    for (int i = 0; i < x+1; i++) {
        for (int j = 0; j < y+1; j++) {
            if (i == 0 || j == 0) {
                LCS[i][j] = 0;
//                printf("0 LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
            else if (X[i] == Y[j]) {
                LCS[i][j] = LCS[i-1][j-1] + 1;
//                printf("1 LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
            else {
                LCS[i][j] = (LCS[i-1][j] > LCS[i][j-1]) ? LCS[i-1][j] : LCS[i][j-1]; 
//                printf("LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
        }
    }

    return LCS[x][y]; 
}

int main() {
    int q;
    int x;
    int y;

    cin >> q;

    for (int i = 0; i < q; i++) {
        scanf("%s", X);
        x = strlen(X);
        scanf("%s", Y);
        y = strlen(Y);
        cout << longest(x, y) << endl;
    }
        
    return 0;
}

C++: // 最長共通部分裂問題

#include <bits/stdc++.h>

#define rep(i, a, n)  for(ll i=a; i<n; i++)
#define per(i, a, n)  for(ll i=n-1; i>=a; i--)
#define fill0(n)  setfill('0') << right << setw(n)
#define all(x)  (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define LONGMAX 1e18
#define INTMAX 1000000000

using namespace std;
typedef long long ll;
typedef pair<ll ,ll> P;
const ll mod = 1e9+7;
const long double EPS = 0.0000000001;


int n;
int main(){
	cin >> n;
	for(int a = 0; a < n; a++){
		string x,y;
		cin >> x;
		cin >> y;

		// dp start
		int W = x.size(); int H = y.size();
		int dp[H+1][W+1] = {0};
		for(int i = 0; i < H+1; i++){
			dp[i][0] = 0;
		}
		for(int i = 0; i < W+1; i++){
			dp[0][i] = 0;
		}
		for(int i = 1; i < H+1; i++){
			for(int j = 1; j < W+1; j++){
				if(x[j-1] == y[i-1]){
					dp[i][j] = max(max(dp[i-1][j-1] + 1, dp[i-1][j]), dp[i][j-1]);
				}else{
					dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
				}
			}
		}
		// cout << endl;
		// for(int i = 0; i < H+1; i++){
		// 	for(int j = 0; j < W+1; j++){
		// 		cout << dp[i][j] << " ";
		// 	}
		// 	cout << endl;
		// }

		cout << dp[H][W] << endl;
	}
}