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 <math.h>
#include <string>
#include <algorithm>
#include <set>
#include <queue>
#include <stack>
#include <utility>
#include <tuple>
using namespace std;

const double pi = acos(-1);
#define nyan cout<<"(=^•ω•^=)"<<endl;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)

int Q;
int dp[1100][1100];
// 1-leadingとして，
// dp[i][j] := sのi番目までの文字列とtのj番目までの文字列のLCSのサイズ

signed main(){
    cin>>Q;
    rep(q,Q){
        string s,t;
        cin>>s>>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-1][j],dp[i][j-1]);
            }
        }
        cout<<dp[s.length()][t.length()]<<endl;
    }
    return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace std;
 
static const long N = 1000;
 
long lcs(string X, string Y){
    long c[N + 1][N + 1];
    long m = X.size();
    long n = Y.size();
    long maxl = 0;
    X = ' ' + X;
    Y = ' ' + Y;
    for (long i = 1; i <= m; i++) c[i][0] = 0;
    for (long j = 1; j <= n; j++) c[0][j] = 0;
 
    for (long i = 1; i <= m; i++){
        for (long 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;
    long n;
    cin >> n;
    for (long i = 0; i < n; i++){
        cin >> s1 >> s2;
        cout << lcs(s1, s2) << endl;
    }
    return 0;
}

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

int h[1001][1001];
string A;
string B;

void f(int i, int j) {
    if (A.at(i) == B.at(j)) {
            h[i][j] = h[i-1][j-1] + 1;
    } else {
        h[i][j] = max(h[i][j-1], h[i-1][j]);
    }
}

int lcs(string A, string B) {
    for (int i = 1; i <= A.length()-1; ++i) {
        for (int j = 1; j <= B.length()-1; ++j) {
            f(i, j);
        }

    }
    return h[A.length()-1][B.length()-1];
}

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

    for (int i = 0; i < n; ++i) {
        cin >> A;
        cin >> B;
        A = " " + A;
        B = " " + B;
        int a = lcs(A, B);
        cout << a << endl;
    }

    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int lcs(string a,string b){
  int c[1001][1001];
  for(int i=0;i<1001;i++){
      for(int j=0;j<1001;j++){
          c[i][j]=0;    
      } 
  }
  int m=a.size(),n=b.size();
  int mx=0;
  a=' '+a;
  b=' '+b;
  for(int i=1;i<=m;i++){
    for(int j=1;j<=n;j++){
      if(a[i]==b[j]){
	c[i][j]=c[i-1][j-1]+1;
      }else{
	c[i][j]=max(c[i-1][j],c[i][j-1]);
      }
      mx=max(mx,c[i][j]);
    }
  }
  return mx;
}


int main(){
  int q;
  string s1,s2;
  cin>>q;
  for(int i=0;i<q;i++){
    cin>>s1>>s2;
    cout<<lcs(s1,s2)<<endl;
  }
  return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
#define N 1050
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=0;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=max(maxl,c[i][j]);
    }
  }
  return maxl;
}
int main(){
  int q;cin>>q;
  while(q--){
    string a,b;cin>>a>>b;
    cout<<lcs(a,b)<<endl;
  }
  return 0;
}

C++: #include <iostream>

using namespace std;

int lcs(string X, string Y) {
  int memo[1010][1010];
  int maxl = 0;

  // 初期化、境界条件を考慮して場合分け
  for (int i = 0; i < X.size(); i++) {
    if (X[i] == Y[0]) {
      memo[i][0] = 1;
    } else {
      memo[i][0] = 0;
    }
  }

  for (int j = 0; j < Y.size(); j++) {
    if (X[0] == Y[j]) {
      memo[0][j] = 1;
    } else {
      memo[0][j] = 0;
    }
  }

  for (int i = 0; i < X.size(); i++) {
    for (int j = 0; j < Y.size(); j++) {
      if (X[i] == Y[j]) {
        memo[i][j] = memo[i-1][j-1] + 1;
      } else {
        memo[i][j] = max(memo[i-1][j], memo[i][j-1]);
      }
      maxl = max(maxl, memo[i][j]);
      //cout << i << "," << j << "," << X[i] << "," << Y[j] << "," << maxl << endl;
    }
  }
  return maxl;
}

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

C++: #include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int kMax = 1000 + 10;

char a_str[kMax], b_str[kMax];
int dp[kMax][kMax];

int main() {
    int q;
    scanf("%d", &q);
    while(q --) {
        scanf("%s%s", a_str, b_str);
        int n = strlen(a_str), m = strlen(b_str);
        for(int i = 0;i < n;++ i) {
            for(int j = 0;j < m;++ j) {
                if(a_str[i] == b_str[j]) dp[i][j] = (i && j ? (dp[i-1][j-1] + 1) : 1);
                else dp[i][j] = max(i ? dp[i-1][j] : 0, j ? dp[i][j-1] : 0);
            }
        }
        printf("%d\n", dp[n-1][m-1]);
    }
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int LCS(string &X, string &Y) {
  X = " " + X;
  Y = " " + Y;
  int X_size = X.size(), Y_size = Y.size();
  vector<vector<int>> CS(Y_size, vector<int>(X_size, 0));
  for (int i = 0; i < Y_size; i++) {
    for (int j = 0; j < X_size; j++) {
      if (i == 0 || j == 0) continue;
      else if (X[j] == Y[i]) {
        CS[i][j] = CS[i - 1][j - 1] + 1;
      } else {
        CS[i][j] = max(CS[i][j - 1], CS[i - 1][j]);
      }
    }
  }
  return CS[Y_size - 1][X_size - 1];
}
int main() {
  int q;
  cin >> q;
  string X, Y;
  for (size_t i = 0; i < q; i++) {
    cin >> X >> Y;
    cout << LCS(X, Y) << endl;

    X.clear();
    Y.clear();
  }
}

C++: #include <bits/stdc++.h>
using namespace std;

int dp[1005][1005];
int q,n,m;
string x,y;

int main() {
	cin >> q;
	for(int a = 0; a < q; a++){
		cin >> x >> y;
		n = x.size();
		m = y.size();
		for(int i = 0; i < n; i++){
			for(int j = 0; j < m; j++){
			if		(x[i] == y[j]) dp[i+1][j+1] = dp[i][j] + 1;
			else if (x[i] != y[j]) dp[i+1][j+1] = max(dp[i][j+1],dp[i+1][j]);
			}
		}
		cout << dp[n][m] << endl;
	}
}