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 <cstdio>
#include <algorithm>
#include <string>
#include <cstring>
#include <cctype>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <stdio.h>
#include <string.h>
#include <cstdlib>
#include <math.h>
#include <bitset>
#include <iterator>
#include <iomanip>
#include <sstream>
#define INF 2000000000
using namespace std;
int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
#define sym cout<<"---------"<<endl;
#define ll long long
#define PL pair<long long, long long>
#define P pair<int,int>
#define mk make_pair
#define en endl
#define WHITE 0
#define BLACK 2
#define GRAY 1
#define RE return 0
#define int ll
//
//vector<int> G[20];
//
//// 巡回セールスマン問題
//
//signed main(){
//  int v,e;
//  cin>>v>>e;
//
//  for(int i=0; i<e; i++){
//    int a,b;
//    cin>>a>>b;
//    G[a].push_back(b);
//  }
//}























////  最長共通部分列

int dp[1005][1005];

signed main(){
  int n;
  cin>>n;
  for(int i=0; i<n; i++){
    string s1,s2;
    cin>>s1>>s2;
    s1=" "+s1;
    s2=" "+s2;
    int maxl=0;
    for(int i=0; i<=s1.size()-1; i++) for(int j=0; j<=s2.size(); j++) dp[i][j]=0;
    for(int i=1; i<=s1.size()-1; i++){
      for(int j=1; j<=s2.size(); j++){
        if(s1[i]==s2[j]) dp[i][j]=dp[i-1][j-1]+1;
        else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
        maxl=max(maxl,dp[i][j]);
      }
    }
    cout<<maxl<<en;
  }
}

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

static const int N = 1000;

int max(int a, int b)
{
	if(a > b)
		return a;
	else 
		return b;
}
int lcs(string X, string Y)
{
	int c[N+1][N+1] = {0};
	int m = X.size();
	int n = Y.size();

	int max1 = 0;
	X = ' ' + X;
	Y = ' ' + Y;

	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 a,b;
	int n;
	scanf("%d", &n);
	for(int i=0; i<n; i++)
	{
		cin >> a >> b;
		printf("%d\n",lcs(a,b));
	}

	return 0;
}

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

int lcs(string X, string Y) {
	int dp[1000 + 1][1000 + 1];
	int max = 0;
	X = ' ' + X;
	Y = ' ' + Y;
	for (unsigned int i = 1; i <= X.length() - 1; i++)
		dp[i][0] = 0;

	for (unsigned int i = 1; i <= Y.length() - 1; i++)
		dp[0][i] = 0;

	for (unsigned int i = 1; i <= X.length() - 1; i++) {
		for (unsigned int j = 1; j <= Y.length() - 1; j++) {
			if (X[i] == Y[i])
				dp[i][j] = dp[i - 1][j - 1] + 1;
			else if (dp[i - 1][j] >= dp[i][j - 1])
				dp[i][j] = dp[i - 1][j];
			else
				dp[i][j] = dp[i][j - 1];

			max = (max < dp[i][j]) ? dp[i][j] : max;
        cout << "Hello" << endl;
		}
	}

	return max;
}

int main() {
	int N;
	cin >> N;

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

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

	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

int dp[1010][1010];

int main(void) {
    int q;
    string x, y;
    cin >> q;

    while (cin >> x >> y) {
        memset(dp, 0, sizeof dp);

        int xs = x.size(), ys = y.size();
        for (int i = 1; i <= xs; i++)
            for (int j = 1; j <= ys; 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], max(dp[i][j - 1], dp[i - 1][j - 1]));
            }
            
        cout << dp[xs][ys] << endl;
    }

    return 0;
}

C++: #include <bits/stdc++.h>
 
#define REP(i, n) for(int i=0;i<(int)(n);i++)
#define ALL(x) (x).begin(),(x).end()
const int INF = 1e9;
 
using namespace std;
int dp[1005][1005];
 
int main() {
    int n; cin >> n;
    REP(k, n){
        REP(i, 1005) REP(j, 1005) dp[i][j] = 0;
        string a, b;
        cin >> a >> b;
        REP(i, a.length()){
            string q = a.substr(i, 1);
            REP(j, b.length()){
                string t = b.substr(j, 1);
                if(q == t){
                    if(i == 0 || j == 0)
                        dp[i][j] = 1;
                    else
                        dp[i][j] = (dp[i-1][j] > dp[i][j-1]) ? max(dp[i-1][j-1] + 1, dp[i-1][j]) : max(dp[i-1][j-1] + 1, dp[i][j-1]);
                }
                else if (i != 0 && j != 0)
                    dp[i][j] = (dp[i-1][j] > dp[i][j-1]) ? dp[i-1][j] : dp[i][j-1];
                else if (i != 0)
                    dp[i][j] = dp[i-1][j];
                else
                    dp[i][j] = dp[i][j-1];
            }
        }
        cout << dp[a.length()-1][b.length()-1] << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <bitset>
#include <climits>
#define REP(i,n) for (int i=0;i<(n);i++)
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define RFOR(i,a,b) for (int i=(a)-1;i>=(b);i--)
#define ll long long
#define ull unsigned long long
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
const int INF = 1e9;
const int MOD = 1e9 + 7;

using namespace std;
int dp[1000][1000];
int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
	int n;
	cin>>n;
	string s1,s2;
	while(n--){
		cin>>s1>>s2;
		REP(i,s1.size())dp[i][0] = 0;
		REP(i,s2.size())dp[0][i] = 0;
		FOR(i,1,s1.size()+1){
			FOR(j,1,s2.size()+1){
				if(s1[i] == s2[j])dp[i][j] = dp[i-1][j-1]+1;
				else dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
			}
		}
		cout << dp[s1.size()][s2.size()] << endl;
	}
  return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace 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 = 1; 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 = C[i][j];
        }
    }
    return maxl;
}


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;
}