Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	for i := 0; i < n; i++ {
		x := getNextString(scanner)
		y := getNextString(scanner)

		fmt.Fprintln(writer, lcs(x, y))
	}

	writer.Flush()
}

func lcs(x, y string) int {
	lx := len(x)
	ly := len(y)
	dp := make([][]int, lx+1)
	for i := 0; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
	}
	for i := 0; i < lx; i++ {
		for ii := 0; ii < ly; ii++ {
			if x[i] == y[ii] {
				dp[i+1][ii+1] = dp[i][ii] + 1
				continue
			}
			dp[i+1][ii+1] = dp[i][ii+1]
			if dp[i+1][ii] > dp[i+1][ii+1] {
				dp[i+1][ii+1] = dp[i+1][ii]
			}
		}
	}
	return dp[lx][ly]
}

C++: #include<iostream>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i,n) for(int i=0;i<n;i++)
using P = pair<int,int>;

/* 大文字を小文字に変換 */
char tolower(char c) {return (c + 0x20);}
/* 小文字を大文字に変換 */
char toupr(char c) {return (c - 0x20);}

// if('A'<=s[i] && s[i]<='Z') s[i] += 'a'-'A';

/*
string s = "abcdefg"
s.substr(4) "efg"
s.substr(0,3) "abc"
s.substr(2,4) "cdef"

// イテレータ要素のインデックス
distance(A.begin(), itr);
*/

int lcs(string X, string Y){
    int n = X.size(), m = Y.size();
    int lcsv[n+1][m+1];
    rep(i,n+1) lcsv[i][0] = 0;
    rep(j,m+1) lcsv[0][j] = 0;
    rep(i,n){
        rep(j,m){
            if(X[i] == Y[j]){
                lcsv[i+1][j+1] = lcsv[i][j]+1;
            }else{
                lcsv[i+1][j+1] = max(lcsv[i+1][j], lcsv[i][j+1]);
            }
        }
    }
    return lcsv[n][m];
}

int main()
{
    int n; cin >> n;
    rep(_,n){
        string X, Y; cin >> X >> Y;
        cout << lcs(X, Y) << endl;
    }
}

C++: #include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <string>
#include <cstring>
#include <complex>
#include <ctime>
#include <cstdlib>

using namespace std;

inline int to_int(string s) {int v; istringstream sin(s); sin >> v; return v;}
template<class T> inline string to_str(T x) {ostringstream sout; sout << x; return sout.str();}

typedef long long ll;

int main()
{
	int n, dp[1024][1024];
	string a, b;
	cin >> n;
	
	while(n)
	{
		n--;
		memset(dp, 0, sizeof(dp));

		cin >> a;
		cin >> b;

		for(int i = 0; i <= a.size(); i++)
		{
			for(int j = 0; j <= b.size(); j++)
			{
				if(a[i+1] == b[j+1])
				{
					dp[i+1][j+1] = dp[i][j] + 1;
				}
				else
				{
					dp[i+1][j+1] = max(dp[i+1][j], dp[i][j+1]);
				}
			}
		}

		cout << dp[a.size()+1][b.size()+1] << endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vs = vector<string>;
using msi = map<string, int>;
using mii = map<int, int>;
using psi = pair<string, int>;
using pii = pair<int, int>;
using vlai = valarray<int>;
#define rep(i,n) for(int i=0;i<n;i++)
#define range(i,s,n) for(int i=s;i<n;i++)
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define INF 1E9
#define EPS 1E-9
#define MOD (1E9+7)
#define PI 3.1415926535897932384626433832795

std::ostream &operator<<(std::ostream &out, const vector<int> &tgt)
{
	string s;
	for (int i = 0; i<tgt.size(); i++) {
		s += (to_string(tgt[i]) + ((i != tgt.size() - 1) ? " " : ""));
	}
	out << s;
	return out;
}

void solve(string a, string b) {
	vvi dp(a.size()+1, vi(b.size()+1,0));
	for (int i = 1; i < dp.size(); i++) {
		for (int j = 1; j < dp[0].size(); j++) {
			if (a[i - 1] == b[j - 1]) {
				dp[i][j] = dp[i - 1][j - 1] + 1;
			}
			else {
				dp[i][j] = max(dp[i][j - 1], dp[i - 1][j]);
			}
		}
	}
	cout << dp[a.size()][b.size()] << endl;
}

int main() {
	int n;
	cin >> n;
	string a, b;
	rep(i, n) {
		cin >> a >> b;
		solve(a, b);
	}
}

C++: #include <iostream>
#include <vector>
using namespace std;

int main () {
    int N;
    cin >> N;
    vector<string> S(N), T(N);
    for (int i = 0; i < N; i++)
        cin >> S[i] >> T[i];

    for (int i = 0; i < N; i++) {
        int dp[1001][1001] = {};
        string s = S[i], t = T[i];
        int n = s.size(), m = t.size();
        for (int j = 0; j < n; j++) {
            for (int k = 0; k < m; k++) {
                if (s[j] == t[k]) {
                    dp[j + 1][k + 1] = dp[j][k] + 1;
                } else {
                    dp[j + 1][k + 1] = max(dp[j + 1][k], dp[j][k + 1]);
                }
            }
        }
        cout << dp[n][m] << endl;
    }
    return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
int main(){
  char str1[1000],str2[1000];
  int LCS[1000][1000]={0};
  int length1,length2;
  int n;
  std::ios::sync_with_stdio(false);
  scanf("%d",&n);
  for(int s=1;s<=n;s++){
   while(cin>>str1>>str2){
     length1=strlen(str1);
     length2=strlen(str2);
     for(int i=0;i<=length1-1;i++){
       LCS[i][0]=0;
     }
     for(int j=0;j<=length2-1;j++){
       LCS[0][j]=0;
     }
     for(int i=1;i<=length1;i++){
       for(int j=1;j<=length2;j++){
         if(str1[i-1]==str2[j-1]) {
           LCS[i][j]=LCS[i-1][j-1]+1;
         }
         else LCS[i][j]=max(LCS[i-1][j],LCS[i][j-1]);
       }
     }
     printf("%d\n",LCS[length1][length2]);
   }
 }
   return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define INF 100000000000
const int MOD = 1000000009;

//マクロ
#define FOR(i, a, b) for(int i = (a); i < (b), i++)
#define REP(i, n) FOR(i, 0, n);
#define ALL(a) (a).begin(),(a).end()

// 最長共通部分列問題
// 入力
// S T

// dp[i + 1][j + 1] := Sのi文字目までと、Tのj文字目までのLCSの長さ
// 計算量 O(|S||T|)

int main(){

    //入力
    int n; cin >> n;
    for(int roop = 0; roop < n; roop++){
        string S, T; cin >> S >> T;
        vector<vector<int> > dp(S.size() + 1, vector<int> (T.size() + 1, INF));

        //dp初期条件
        dp[0][0] = 0;

        //dp
        for(int i = 0; i < S.size(); i++){
            for(int j = 0; j < T.size(); j++){
                if(S[i] == T[j]) dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i + 1][j]);
                dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j + 1]);
            }
        }

        cout << dp[S.size()][T.size()];
        return 0;
    }
}