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++: #define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
//#include "libs.h"
#include <random>
#include <unordered_map>
#include <unordered_set>
//#include <opencv2/core.hpp>
//#include <opencv2/highgui.hpp>
//#include <opencv2/imgproc.hpp>

using namespace std;

//呪文
#define DUMPOUT cerr
#define dump(...) DUMPOUT<<"  ";DUMPOUT<<#__VA_ARGS__<<" :["<<__LINE__<<":"<<__FUNCTION__<<"]"<<endl;DUMPOUT<<"    ";dump_func(__VA_ARGS__)

typedef unsigned uint; typedef long long ll; typedef unsigned long long ull; typedef pair<int, int> pii; typedef pair<ll, ll> pll; typedef pair<double, double> pdd; typedef pair<string, string> pss;
template <typename _KTy, typename _Ty> ostream& operator << (ostream& o, const pair<_KTy, _Ty>& m) { o << "{" << m.first << ", " << m.second << "}"; return o; }
template <typename _KTy, typename _Ty> ostream& operator << (ostream& o, const map<_KTy, _Ty>& m) { if (m.empty()) { o << "{ }"; return o; } o << "{" << *m.begin(); for (auto itr = ++m.begin(); itr != m.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _KTy, typename _Ty> ostream& operator << (ostream& o, const unordered_map<_KTy, _Ty>& m) { if (m.empty()) { o << "{ }"; return o; } o << "{" << *m.begin(); for (auto itr = ++m.begin(); itr != m.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const vector<_Ty>& v) { if (v.empty()) { o << "{ }"; return o; } o << "{" << v.front(); for (auto itr = ++v.begin(); itr != v.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const set<_Ty>& s) { if (s.empty()) { o << "{ }"; return o; } o << "{" << *(s.begin()); for (auto itr = ++s.begin(); itr != s.end(); itr++) { o << ", " << *itr; } o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const unordered_set<_Ty>& s) { if (s.empty()) { o << "{ }"; return o; } o << "{" << *(s.begin()); for (auto itr = ++s.begin(); itr != s.end(); itr++) { o << ", " << *itr; }	o << "}"; return o; }
template <typename _Ty> ostream& operator << (ostream& o, const stack<_Ty>& s) { if (s.empty()) { o << "{ }"; return o; } stack<_Ty> t(s); o << "{" << t.top(); t.pop(); while (!t.empty()) { o << ", " << t.top(); t.pop(); } o << "}";	return o; }
template <typename _Ty> ostream& operator << (ostream& o, const list<_Ty>& l) { if (l.empty()) { o << "{ }"; return o; } o << "{" << l.front(); for (auto itr = ++l.begin(); itr != l.end(); ++itr) { o << ", " << *itr; } o << "}"; return o; }
template <typename _KTy, typename _Ty> istream& operator >> (istream& is, pair<_KTy, _Ty>& m) { is >> m.first >> m.second; return is; }
template <typename _Ty> istream& operator >> (istream& is, vector<_Ty>& v) { for (size_t i = 0; i < v.size(); i++) is >> v[i]; return is; }
namespace aux { // print tuple
	template<typename Ty, unsigned N, unsigned L> struct tp { static void print(ostream& os, const Ty& v) { os << get<N>(v) << ", "; tp<Ty, N + 1, L>::print(os, v); } };
	template<typename Ty, unsigned N> struct tp<Ty, N, N> { static void print(ostream& os, const Ty& v) { os << get<N>(v); } };
}
template<typename... Tys> ostream& operator<<(ostream& os, const tuple<Tys...>& t) { os << "{"; aux::tp<tuple<Tys...>, 0, sizeof...(Tys)-1>::print(os, t); os << "}"; return os; }

template<typename A, size_t N, typename T> inline void Fill(A(&array)[N], const T &val) { std::fill((T*)array, (T*)(array + N), val); }

void dump_func() { DUMPOUT << endl; }
template <class Head, class... Tail> void dump_func(Head&& head, Tail&&... tail) { DUMPOUT << head; if (sizeof...(Tail) == 0) { DUMPOUT << " "; } else { DUMPOUT << ", "; } dump_func(std::move(tail)...); }

#define PI 3.14159265358979323846
#define EPS 1e-10
#define FOR(is,a,n) for(int is=(a);is<(n);++is)
#define REP(is,n)  FOR(is,0,n)
#define all(j) (j).begin(), (j).end()
#define SZ(j) ((int)(j).size())
#define fake false



int LCS(const string& X, const string& Y) {
	int n = X.size(), m = Y.size();
	vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			if (X[i - 1] == Y[j - 1])
				dp[i][j] = dp[i - 1][j - 1] + 1;
			else
				dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
		}
	}
	return dp[n][m];
}

int main() {
	
	cin.tie(0);
	ios::sync_with_stdio(false);

	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		string X, Y;
		cin >> X >> Y;

		cout << LCS(X, Y) << endl;
	}

	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;int l(string a,string b){int m=a.size(),n=b.size(),i=0,j,s=0,c[1001][1001]={};for(a=' '+a,b=' '+b;++i<=m;)for(j=0;++j<=n;s=s<c[i][j]?c[i][j]:s)c[i][j]=a[i]==b[j]?c[i-1][j-1]+1:c[i-1][j]>c[i][j-1]?c[i-1][j]:c[i][j-1];return s;}main(){string a,b;int n;for(cin>>n;n--;)cin>>a>>b,cout<<l(a,b)<<endl;}

C++: using namespase std;
static const int N = 1000;

int lcs( string X, string Y ) {
    int c[N + 1][N + 1];
    int m = X.size();
    int n = Y.size();
    int maxl = 0;
    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 - 1][j], c[i][j - 1]);
            }
            maxl = max(maxl, c[i][j]);
        }
    }
    return maxl;
}

int main() {
    string s1, s2;
    int n; cin >> n;
    for ( i = 0; i < n; i++ ){
        cin >> s1 >> s2;
        cout << lcs(s1, s2) << sndl;
    }
    
    return 0;
    
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
 
int lcs(string x, string y) {
    static int c[1001][1001];
    int m = x.size();
    int n = y.size();
    int max1 = 0;
    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 - 1][j], c[i][j - 1]);
            max1 = max(max1, c[i][j]);
 
        }
    }
    return max1;
}
 
int main() {
    string s1, s2;
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> s1 >> s2;
        cout << lcs(s1, s2) << endl;
    }
    return 0;
}