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 <vector>
#include <map>
#include <algorithm>
#include <set>
#include <queue>
#include <string>
#include <tuple>
using namespace std;

int solve(string& X, string& Y){
  int x_size = X.size();
  int y_size = Y.size();
  
  vector<vector<int>> dp(y_size+1);
  for(int i=0;i<=y_size;i++){
    for(int j=0;j<=x_size;j++){
      dp[i].push_back(0);
    }
  }
  
  for(int i=1;i<=y_size;i++){
    for(int j=1;j<=x_size;j++){
      if(Y[i-1]==X[j-1]){
        dp[i][j] = dp[i-1][j-1]+1;
      } else {
        dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
      }
    }
  }
  
  /*
  for(int i=0;i<=y_size;i++){
    for(int j=0;j<=x_size;j++){
      cout << dp[i][j] << " ";
    }
    cout << endl;
  }
  */
  
  return dp[y_size][x_size];
}

int main(void){
  int N;
  cin >> N;
  for(int i=0;i<N;i++){
    string X,Y;
    cin >> X >> Y;
    
    int lcs = solve(X,Y);
  
    cout << lcs << endl;
  }
}

C++: #include <bits/stdc++.h>
 
#define rep(i,n) for(ll i=0;i<n;++i)
#define ALL(a) (a).begin(),(a).end()
 
using namespace std;
using ll  = long long;
using pll = pair<ll, ll>;
 
const ll MOD  = 1e9+7;
const ll LINF = 1LL << 60;
const int INF = 1e9 + 7;

int solve(string x, string y){
    //dp[i][j] xの i文字目、yのj文字目までの最長共通部分列の長さ
    int dp[1010][1010] = {};

    rep(i, x.size())rep(j, y.size()){
        dp[i+1][j+1] = max(dp[i+1][j], dp[i][j+1]);
        if(x[i] == y[j])dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j]+1);
    }

    return dp[x.size()][y.size()];
}
int main(){
    int q;
    cin >> q;

    int ans[q];

    rep(i, q){
        string x, y;
        cin >> x >> y;
        
        ans[i] = solve(x, y);
    }

    rep(i, q)cout << ans[i] << endl;
}

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

const int N = 1000;

int lcs(string a, string b) {
  int C[N+1][N+1];
  int n = a.size();
  int m = b.size();
  for (int i = 0; i <= n; i++) C[i][0] = 0;
  for (int i = 0; i <= m; i++) C[0][i] = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      if (a[i-1] == b[j-1]) {
        C[i][j] = C[i-1][j-1] + 1;
      } else {
        C[i][j] = C[i][j-1] > C[i-1][j] ? C[i][j-1] : C[i-1][j];
      }
    }
  }
  return C[n][m];
}

int main() {
  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<iostream>
#include<cstdio>
#include<string>
#include<algorithm>

using namespace std;

int N=1000;

int LCS(string x,string y){
	int c[N+1][N+1],LCSlen=0;
	int m=x.size();
	int n=y.size();
	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][j-1],c[i-1][j]);
			LCSlen=max(LCSlen,c[i][j]);
		}
	}
	return LCSlen;
}

int main(){
	string x,y;
	int n;
	scanf("%d",&n);
	for(int i=0;i<n;i++){
		cin>>x;
		cin>>y;
		printf("%d\n",LCS(x,y));
	}
}

C++: #include <cstdio>
#include <iostream>
#include <cmath>
#include <ctype.h>
#include <string> 
#include <sstream>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <map>
#include <queue>
#include <utility>
#include <vector>
#include <set>
#include <iomanip>
  
using namespace std;

#define pi 3.141592653589793

int solve(string s1, string s2, int l1, int l2)
{
	if(l1 == -1 || l2 == -1) return 0;
	else if(s1[l1] == s2[l2]) return solve(s1, s2, l1 - 1, l2 - 1) + 1;
	else return max(solve(s1, s2, l1, l2 - 1), solve(s1, s2, l1 - 1, l2));
}

int main()
{
	int q;
	cin >> q;
	for(int i = 0; i < q; i++){
		string s1, s2;
		cin >> s1 >> s2;
		cout << solve(s1, s2, s1.length() - 1, s2.length() - 1) << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<(b);++i)
#define erep(i,a,b) for(int i=a;i<=(int)(b);++i)
#define per(i,a,b) for(int i=(b);i>(a);--i)
#define eper(i,a,b) for(int i=((int)(a));i>=b;--i)
#define pb push_back
#define mp make_pair
#define INF (1<<30)-1
#define MOD 1000000007
#define all(x) (x).begin(),(x).end()
using namespace std;
typedef long long ll;
typedef pair<int,int> Pii;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0};
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a/gcd(a, b)*b;}

string s, t;
int dp[1010][1010];
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
    int n;
    cin >> n;
    rep(i, 0, n) {
        memset(dp, 0, sizeof(dp));
        cin >> s >> t;
        erep(i, 0, s.size()) {
            erep(j, 0, t.size()) {
                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[s.size()][t.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;  // X[0] に空白を挿入
  Y = ' ' + Y;  // Y[0] に空白を挿入
  for ( int i = 1; i <= m; i++ ) c[i][0] = 0;
  for ( int j = 1; j <= m; j++ ) c[0][j] = 0;

  for ( int i = 1; i <= m; i++ )
    for ( int j = 1; j <= m; 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 ( int i = 0; i < n; i++ ) {
    cin >> s1 >> s2;
    cout << lcs(s1, s2) << endl;
  }
  return 0;
}