Go: package main

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

const (
	initialBufSize = 100000
	maxBufSize     = 1000000
)

var sc *bufio.Scanner

func initScanner(r io.Reader) *bufio.Scanner {
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	return sc
}

func main() {
	sc = initScanner(os.Stdin)
	resolve()
}

func resolve() {
	n := scanInt(sc)
	results := []int{}
	for i := 0; i < n; i++ {
		results = append(results, resolveInstance())
	}
	for _, v := range results {
		fmt.Println(v)
	}
	return
}

func resolveInstance() int {
	x, y := scanString(sc), scanString(sc)
	lx, ly := len(x), len(y)
	dp := make([][]int, lx+1)
	dp[0] = make([]int, ly+1)
	for i := 1; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
		dp[i][0] = dp[i-1][0]
		for j := 1; j <= ly; j++ {
			dp[i][j] = dp[i-1][j]
			if dp[i][j] < dp[i][j-1] {
				dp[i][j] = dp[i][j-1]
			}
			if x[i-1] == y[j-1] {
				cL := dp[i-1][j-1] + 1
				if dp[i][j] < cL {
					dp[i][j] = cL
				}
			}
		}
	}
	return dp[lx][ly]
}

const (
	remove = 0 + iota
	match
)

// snip-scan-funcs
func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return int(i)
}
func scanString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: #include <iostream>
#include <string>
using namespace std;
int main(void){
    int n;
    cin >> n;
    for(int i = 0;i < n;i++){
        string X,Y;
        cin >> X >> Y;
        int L[X.length()+10][Y.length()+10];
        for(int j = 0;j < X.length()+10;j++){
            for(int k = 0;k < X.length()+10;k++){
                L[j][k] = 0;
            }
        }
        for(int j = 1;j<=X.length();j++){
            for(int k = 1;k<=Y.length();k++){
                if(Y[k] == X[j]){
                    L[j][k] = 1+L[j-1][k-1];
                }
                else{
                    L[j][k] = max(L[j-1][k],L[j][k-1]);
                }
            }
        }
        cout << L[X.length()][Y.length()] << endl;
    }
}

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

int main(){
    int q;
    cin >> q;
    int dp[1001][1001] = {0};
    for(int i = 0; i < q; i++){
        bool flagx[1001] = {0}, flagy[1001] = {0};
        string S1, S2;
        cin >> S1 >> S2;
        const int m = S1.size();
        const int n = S2.size();
        for(int j = 0; j < m; j++){
            for(int k = 0; k < n; k++){
                if(j == 0 && k == 0) dp[j][k] = 0;
                else if(j == 0) dp[j][k] = dp[j][k-1];
                else if(k == 0) dp[j][k] = dp[j-1][k];
                else{
                    dp[j][k] = max(dp[j-1][k],dp[j][k-1]);
                }
                if(S1[j] == S2[k] && !flagx[j] && !flagy[k]) {
                    //cout << j << " " << k << " " << dp[j][k]++ <<endl;
                    dp[j][k]++;
                    flagx[j] = 1;
                    flagy[k] = 1;
                }
            }

        }
        cout << dp[m-1][n-1] << endl;
    }
}

C++: #include <iostream>
#include <cstring>
#include <algorithm>
#include <string>
using namespace std;

int q;
string X, Y;


int main(void) {
  int dp[1000][1000];
  cin >> q;
  for (int i = 0; i < q; i++) {
    cin >> X >> Y;

    dp[0][0] = X[0] == Y[0];
    for (int j = 1; j < Y.size(); j++) dp[0][j] = dp[0][j-1] || X[0] == Y[j];
    for (int j = 1; j < X.size(); j++) dp[j][0] = dp[j-1][0] || X[j] == Y[0];

    for (int j = 1; j < X.size(); j++) {
      for (int k = 1; k < Y.size(); k++) {
        if (X[j] == Y[k]) {
          dp[j][k] = dp[j-1][k-1] + 1;
        } else {
          dp[j][k] = max(dp[j-1][k], dp[j][k-1]);
        }
      }
    }

    cout << dp[X.size()-1][Y.size()-1] << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>

using namespace std;

typedef pair<int,int> pii;

vector<pii> P;

string s,t,rev;

const int MAX_N = 1001;

int dp[MAX_N][MAX_N];

void trace(int i,int j){
	if(dp[i][j] == dp[i-1][j] && dp[i][j] == dp[i][j-1]){
		trace(i-1,j-1);	//??????????§????
	}else if(dp[i][j] == dp[i-1][j]){
		trace(i-1,j);	//???????§????
	}else if(dp[i][j] == dp[i][j-1]){
		trace(i,j-1);	//???????§????
	}else{
		rev += s[i-1];
		if(dp[i-1][j-1] == 0){
			return;
		}
		trace(i-1,j-1);	//??????????§????
	}
}
int main()
{
	string com;
	int n;
	cin >> n;
	for(int l=0;l<n;l++){
	cin >> s;
	cin >> t;
	for(int i=0;i<=s.length();i++){
		dp[i][0] = 0;
	}
	for(int i=0;i<=t.length();i++){
		dp[0][i] = 0;
	}
	for(int i=1;i<=s.length();i++){
		for(int j=1;j<=t.length();j++){
			if(s[i-1] == t[j-1]){
				dp[i][j] = dp[i-1][j-1]+1;
			}else{
				dp[i][j] = max(dp[i][j-1],dp[i-1][j]);
			}
		}
	}
	printf("%d\n",dp[s.length()][t.length()]);
	}
	/*
	trace(s.length(),t.length());
	for(int i=rev.length();i>0;i--){
		com += rev[i-1];
	}
	cout << com << "\n";	//????????±?????¨???????????????????????????
	*/
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <list>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <cmath>
#include <functional>
#include <fstream>
#include <cstdlib>
typedef long long ll;
const int MOD = 1e9+7;


#define REP(i, N) for (int i = 0; i < (N); i++)
#define REPP(i, a, b) for (int i = (a); i < (b); i++)
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define VSORT(c) sort((c).begin(),(c).end())
#define SZ(x) ((int)(x).size())
//vvintを作る　マクロで　 #define vvint(N,M) vector<vector<int>>

using namespace std;
string x,y;
int LCS[1002][1002];


int searchLCS(int now_x, int now_y){
    // cout << now_x << " : " << now_y << endl;
    if(LCS[now_x+1][now_y+1] > 0) return LCS[now_x+1][now_y+1];
    if(now_x < 0 || now_y < 0) return LCS[now_x+1][now_y+1] = 0;
    if(x[now_x] == y[now_y]){
        return LCS[now_x+1][now_y+1] = searchLCS(now_x-1,now_y-1)+1;
    }else if(now_x >= 0 && now_y >= 0){
        return LCS[now_x+1][now_y+1] = max(searchLCS(now_x-1,now_y),searchLCS(now_x,now_y-1));
    }
    return 0;
}

int main(){
    
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    for(int i = 0; i < n;i++){
        cin >> x;
        cin >> y;
        for(int i = 0; i < x.length()+1;i++){
            for(int l = 0; l < x.length()+1;l++){
                LCS[i][l] = -1;
            }
        }
        cout << searchLCS(x.length()-1,y.length()-1) << endl;
    }
    

    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cassert>
#include <string>
#include <cstring>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <algorithm>

using namespace std;

// ---------------------
// repetition
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)

// debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

// ---------------------
#define INF 922337203685477580
typedef long long ll;

int dp[1000][1000];

int main() {
  int q;
  cin >> q;
  REP(loop, q) {
    char S[1000], T[1000];
    cin >> S >> T;

    REP(i, strlen(S)) {
      REP(j, strlen(T)) {
        dp[i][j] = 0;
      }
    }
    for (int i = 0; i < strlen(S); i++) {
      for (int j = 0; j < strlen(T); j++) {
        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]);
        }
      }
    }
    cout << dp[strlen(S) - 1][strlen(T) - 1] << endl;
  }

  return 0;
}