Go: package main

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

var (
	nstr   func() string
	stdout *bufio.Writer
)

func init() {
	nstr = newReadString(os.Stdin)
	stdout = bufio.NewWriter(os.Stdout)
}

func main() {
	defer stdout.Flush()

	n := nint()
	xList := make([]string, n)
	yList := make([]string, n)

	for i:=0;i<n ;i++  {
		xList[i] = nstr()
		yList[i] = nstr()
	}

	for i := 0; i<n	; i++  {
		fmt.Println(lcs(xList[i], yList[i]))
	}

}

func lcs(x string, y string) int{
	var m = len(x)
	var n = len(y)

	c := make([][]int, m+1)
	for i:= range c{
		c[i] = make([]int, n+1)
	}
	for i:=	1;i<=m ;i++  {
		for j:=1;j<=n ;j++  {
			if x[i-1] == y[j-1]{
				c[i][j] = c[i-1][j-1] + 1
			}else{
				c[i][j] = int(math.Max(float64(c[i-1][j]), float64(c[i][j-1])))
			}


		}
	}
	return c[m][n]

}


func newReadString(ior io.Reader) func() string {
	r := bufio.NewScanner(ior)
	r.Buffer(make([]byte, 1024), int(1e+11))
	r.Split(bufio.ScanWords)

	return func() string {
		if !r.Scan() {
			panic("Scan failed")
		}
		return r.Text()
	}
}

func nint64() int64 {
	i, err := strconv.ParseInt(nstr(), 0, 64)
	if err != nil {
		panic(err.Error())
	}
	return i
}

func nint() int {
	return int(nint64())
}

func getIntSlice(n int) []int {
	b := make([]int, n)
	for i := 0; i < n; i++ {
		b[i] = nint()
	}
	return b
}

func getStringSlice(n int) []string {
	b := make([]string, n)
	for i := 0; i < n; i++ {
		b[i] = nstr()
	}
	return b
}

func gcd(x, y int) int {
	if y == 0 {
		return x
	}
	return gcd(y, x%y)
}

func lcm(x, y int) int {
	return x * y / gcd(x, y)
}

func contains(s []int, e int) bool {
	for _, a := range s {
		if a == e {
			return true
		}
	}
	return false
}

func bin(i int, prefix bool) string {
	i64 := int64(i)

	if prefix {
		return "0b" + strconv.FormatInt(i64, 2)
	} else {
		return strconv.FormatInt(i64, 2)
	}
}

func strReverse(s string) string {
	runes := []rune(s)
	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]
	}

	return string(runes)
}

C++: # define _CRT_SECURE_NO_WARNINGS 1
# define _USE_MATH_DEFINES
# include <iostream>
# include <numeric>
# include <string>
# include <bitset>
# include <vector>
# include <algorithm>
# include <cstdlib>
# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iomanip>
# include <queue>
# include <sstream>
# include <unordered_set>
# include <unordered_map>
# include <climits>
# include <complex>
# include <cmath>
# include <list>
# include <functional>
# include <string>
# include <ctime>
# include <set>
# include <forward_list>
# include <map>
# include <stack>
using namespace std;
# define MP make_pair
# define INF ((int)(1<<25))
# define REP(i,n) for(int i=0;i<(int)n;i++)
# define FOR(i,n) REP(i,n)
# define FORI(i,k,n) for(int i=k;i<(int)n;i++)
# define TORAD 2.0*M_PI/360.0
# define INT(x) int x;cin>>x;
# define STRING(x) string x;cin>>x;
# define STR(x) STRING(x);
# define DOUBLE(x) double x;cin>>x;
# define DBL(x) DOUBLE(x); 
# define ALL(x) begin(x),end(x)
# define RALL(x) (x).rbegin(),(x).rend()
# define DEBUG(x) cout<<#x<<":"<<x<<endl
# define INIT(a) memset(a,-1,sizeof a)
# define CLR(a) memset(a,0,sizeof a)
# define EPS 1e-12
#ifdef _MSC_VER
#include <intrin.h>
#define __builtin_popcount __popcnt
#endif
typedef long long lint;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<int> vi;
typedef vector<lint> vl;
typedef vector<string> vs;
typedef pair<int, int> pii;
typedef pair<int, pii> piii;
//const int dx[4] = { 0,1,0,-1 }, dy[4] = { -1,0,1,0 };
//const int M = 1000000007;
template<class T> void debug(T a) { for ( auto i : a )cout << i << endl; }

string x, y;
int memo[1100][1100];
int dp(int l, int r)
{
	if ( memo[l][r] != -1 )return memo[l][r];
	if ( l == x.size() && r == y.size() )return 0;
	int ans = 0;
	if ( x[l] == y[r] )
		ans = max(ans, dp(l + 1, r + 1) + 1);
	if ( l != x.size() )
		ans = max(ans, dp(l + 1, r));
	if ( r != y.size() )
		ans = max(ans, dp(l, r + 1));
	return memo[l][r] = ans;
}
int main()
{
	INT(n);
	while ( n-- )
	{
		cin >> x >> y;
		INIT(memo);
		cout << dp(0, 0) << endl;
	}
}

C++: #include <iostream> // cout, endl, cin
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque
#include <unordered_map> // unordered_map
#include <iomanip>
#include <unordered_set> // unordered_set
#include <bitset> // bitset
#include <cctype> // isupper, islower, isdigit, toupper, tolower
#include <math.h>
#include <cmath>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
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; }
const int INF = 1001001000;
const int MOD = 1000000007;

long long gcd(long long a, long long b) {
    if (b == 0) return a;
    else return gcd(b, a % b);
}
long long lcm(long long a, long long b) {
    return a * b / gcd(a, b);
}

using Graph = vector<vector<int>>;
//再帰とかグラフを使うときは予めNの最大値のグローバル配列を取っておく
int N;
vector<int> E[200001];
bool shipment[15][15];
vector<bool> seen;
typedef pair<int, int> P;
int D[101];
//頂点状態を表すcolor[]において、0は未訪問、1は訪問中、2は完了を表す。
int color[101];
int find_time = 0;
int dp[1001][1001];

void solve_LCS(string X,string Y) {
    int S = X.size();
    int T = Y.size();
    for (int i = 0; i < S; i++) {
        for (int j = 0; j < T; j++) {
            //同じ文字だったら、max(今まで+1,今までの最大)をする
            if (X[i] == Y[j]) dp[i + 1][j + 1] = max({ dp[i][j] + 1,dp[i + 1][j],dp[i][j + 1] });
            else dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
        }
    }

    cout << dp[S][T] << endl;
}

int main() {
    int Q; cin >> Q;
    vector<string> Xs(Q);
    vector<string> Ys(Q);
    for (int i = 0; i < Q; i++) {
        cin >> Xs.at(i) >> Ys.at(i);
    }
    for (int i = 0; i < Q; i++) {
        solve_LCS(Xs.at(i),Ys.at(i));
    }
}

C++: #include<iostream>
#include<stdio.h>
#include<string>
#include<algorithm>
#define MAX 10001

using namespace std;

int c[MAX][MAX]; 
int n, m;
int maxlengh;

int lcs(string A, string B) {
	maxlengh = 0;
	A = ' ' + A;
	B = ' ' + B;
	n = A.size();
	m = B.size();

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			if (i == 0 || j == 0) {
				c[i][j] = 0;
			}else if(A[i] == B[j]) {
				c[i][j] = c[i - 1][j - 1] + 1;
			}else{
				c[i][j] = max(c[i][j - 1], c[i - 1][j]);
			}maxlengh = max(maxlengh, c[i][j]);
		}
	}
	return maxlengh;
}

int main() {
	int q;
	cin >> q;
	string a, b;
	
	for (int i = 0; i < q; i++) {
		cin >> a >> b;
		cout << lcs(a, b) << endl;
	}
	return 0;
}

C++: //#define		FILE_INPUT_DEFINE
#ifdef		FILE_INPUT_DEFINE
#include	<fstream>
#endif		// FILE_INPUT_DEFINE

#include	<iostream>
#include	<string>
#include	<algorithm>

using namespace std;

#define			MAX		1000
#define			ind(x)		((x) - 1)

int C[MAX][MAX];

int LCS(string &X, string &Y)
{
	int			Xlen = X.length();
	int			Ylen = Y.length();

	for (int i = 0; i <= Xlen; ++i)
	{
		C[i][0] = 0;
	}

	for (int i = 0; i <= Ylen; ++i)
	{
		C[0][i] = 0;
	}

	for (int i = 1; i <= Xlen; ++i)
	{
		for (int j = 1; j <= Ylen; ++j)
		{
			if (X[ind(i)] == Y[ind(j)])
			{
				C[i][j] = C[i - 1][j - 1] + 1;
			}
			else
			{
				C[i][j] = max(C[i - 1][j], C[i][j - 1]);
			}
		}
	}

	return (C[Xlen][Ylen]);
}

int main()
{
#ifdef		FILE_INPUT_DEFINE
	// input from txt
	std::ifstream in(R"(C:\Temp\input.txt)");
	std::cin.rdbuf(in.rdbuf());
#endif		// FILE_INPUT_DEFINE

	string	X, Y;
	int		n;

	cin >> n;
	cin.clear();
	cin.ignore();

	for (int i = 0; i < n; ++i)
	{
		getline(cin, X);
		getline(cin, Y);

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

	return 0;
}