Go: package main

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

var sc = bufio.NewScanner(os.Stdin)

func scanInt() int {
	num, _ := strconv.Atoi(scanString())
	return num
}

func scanString() string {
	sc.Scan()
	return sc.Text()
}

func init() {
	sc.Split(bufio.ScanWords)
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func lcs(a, b string) int {
	lenA := len(a)
	lenB := len(b)
	dp := make([][]int, lenA+1)
	for i := range dp {
		dp[i] = make([]int, lenB+1)
	}

	for i := 1; i <= lenA; i++ {
		for j := 1; j <= lenB; j++ {
			if a[i-1] == b[j-1] {
				dp[i][j] = dp[i-1][j-1] + 1
			} else {
				dp[i][j] = max(dp[i][j-1], dp[i-1][j])
			}
		}
	}
	return dp[lenA][lenB]
}

func main() {
	n := scanInt()
	w := bufio.NewWriter(os.Stdout)
	for i := 0; i < n; i++ {
		a := scanString()
		b := scanString()
		fmt.Fprintln(w, lcs(a, b))
	}
	w.Flush()
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int (i)=(0);(i)<(int)(n);++(i))
using ll = long long;
using P = pair<int, int>;
using namespace std;

template<class T> void vin(vector<T>& v, int n) {
    v.resize(n);
    for (int i = 0; i < n; ++i) {
        cin >> v[i];
    }
}

int n, m;
string s, t;
const int MAX = 1010;

int dp[MAX][MAX];

int rec(int si, int ti) {
    if (dp[si][ti] >= 0) {
        return dp[si][ti];
    }
    int res = 0;
    if (si == n and ti == m) {
        return res;
    }
    else {
        if (s[si] == t[ti]) {
            res = max(res, rec(si + 1, ti + 1) + 1);
        }
        else {
            if (si < n) {
                res = max(res, rec(si + 1, ti));
            }
            if (ti < m) {
                res = max(res, rec(si, ti + 1));
            }
        }
    }
    return (dp[si][ti] = res);
}

void solve() {
    int q;
    cin >> q;
    while (q--) {
        cin >> s >> t;
        n = s.size(), m = t.size();
        fill(dp[0], dp[MAX], -1);
        cout << rec(0, 0) << endl;
    }
}

int main() {
    solve();
}

C++: // longest common subsequence
#include<iostream>
#include<string>
#include<algorithm>
int LCS(std::string, std::string);
int N=1000;
int main(){
  int n;
  std::string str1, str2;
  std::cin >> n;
  for(int i=0; i<n; i++){
    std::cin >> str1 >> str2;
    std::cout << LCS(str1, str2) << std::endl;
  }
  return 0;
}
int LCS(std::string str1, std::string str2){
  int c[N+1][N+1], m=str1.size(), n=str2.size(), maxl=0;
  str1 = ' ' + str1, str2 = ' ' + str2;
  for(int i=1; i<=m; i++) c[i][0] = 0;
  for(int i=1; i<=n; i++) c[0][i] = 0;
  for(int i=1; i<=m; i++){
    for(int j=1; j<=n; j++){
      if(str1[i] == str2[j]) c[i][j] = c[i-1][j-1] + 1;
      else c[i][j] = std::max(c[i-1][j], c[i][j-1]);
      maxl = std::max(maxl, c[i][j]);
    }
  }
  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 = 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() {
  string s1, s2;
  int n; cin >> n;
  for ( int i = 0; i < n; i++ ) {
    cin >> s1 >> s2;
    cout << lcs(s1, s2) << endl;
  }
  return 0;
}

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

#define N 1000

int main(void) {
    int n;
    cin >> n;
    
    for(int k = 0; k < n; ++k) {
        string s1, s2; 
        int max = -1;
        int ans[N + 1][N + 1];
        
        cin >> s1 >> s2;
        
        for(int i = 0; i < s1.length(); ++i) {
            ans[i][0] = 0;
        }
        for(int j = 0; j < s2.length(); ++j) {
            ans[0][j] = 0;
        }
        
        for(int i = 0; i < s1.length(); ++i) {
            for(int j = 0; j < s2.length(); ++j) {
                if(s1[i] == s2[j]) {
                    ans[i + 1][j + 1] = ans[i][j] + 1;
                } else {
                    ans[i + 1][j + 1] = (ans[i][j + 1] > ans[i + 1][j]) ? ans[i][j + 1] : ans[i + 1][j];
                }
                max = (max > ans[i + 1][j + 1]) ? max : ans[i + 1][j + 1];
            }
        }
        
        cout << max << endl;
    }
}

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

int dp[1001][1001];

int main(){
  int q,xl,yl;
  char X[1001],Y[1001];

  cin >> q;

  for (int i=0;i<q;i++){
    cin >> X >> Y;

    xl=strlen(X);
    yl=strlen(Y);
  
    for (int i=1;i<=xl;i++)dp[0][i]=0;
    for (int i=1;i<=yl;i++)dp[i][0]=0;
    for (int i=0;i<yl;i++)
      for (int j=0;j<xl;j++){
	if (X[j]==Y[i]){
	  dp[i+1][j+1]=dp[i][j]+1;
	}else{
	  if (dp[i+1][j]>dp[i][j+1])
	    dp[i+1][j+1]=dp[i+1][j];
	  else
	    dp[i+1][j+1]=dp[i][j+1];	    
	}
      }
    cout << dp[yl][xl]<<endl;
    
  }
  
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#define INF 100000

using namespace std;

int dp[1000][1000];
string X, Y;

int lcs(int i,int j){
  if(i < 0 || j < 0) return 0;
  if(dp[i][j] != INF) return dp[i][j];

  if(X[i] == Y[j]){
    dp[i][j] = lcs(i-1, j-1) + 1;
    return dp[i][j];
  } else {
    dp[i][j] =  max(lcs(i-1,j), lcs(i, j-1));
    return dp[i][j];
  }
}

void clear(){
  for(int i = 0;i < X.size();i++){
    for(int j = 0;j < Y.size();j++){
      dp[i][j] = INF;
    }
  }
}

int main(){
  int q;

  cin >> q;

  for(int i = 0;i < q;i++){
    cin >> X >> Y;
    
    clear();
    
    cout << lcs(X.size()-1, Y.size()-1) << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repr(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, m, n) for (int i = (m); i < (n); ++i)
#define FORR(i, m, n) for (int i = (m); i >= (n); --i)
using namespace std;
typedef long long ll;
const ll mod = 1000000007;
const ll mod2 = 998244353;
const int INF = 1000000005;
const int MAX = 1005;

int lcs[MAX][MAX];

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

  rep(i, q) {
    cin >> x >> y;
    nx = x.size();
    ny = y.size();

    rep(i, nx+1) {
      rep(j, ny+1) {
        lcs[i][j] = 0;
      }
    }

    FOR(i, 1, nx+1) {
      FOR(j, 1, ny+1) {
        if (x[i-1] == y[j-1]) {
          lcs[i][j] = lcs[i-1][j-1] + 1;
        }
        else {
          lcs[i][j] = max(lcs[i-1][j], lcs[i][j-1]);
        }
      }
    }

    cout << lcs[nx][ny] << endl;
  }

  
  return 0;
}

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

using namespace std;

using ll = long long;
using P = pair<ll, ll>;
using Graph = vector<vector<ll>>;
#define rep(i, n) for(ll i=0;i<(ll)(n);i++)
#define rep2(i, m, n) for(ll i=m;i<(ll)(n);i++)
#define rrep(i, n, m) for(ll i=n;i>=(ll)(m);i--)
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const int ddx[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll MOD = 1000000007;
const ll INF = 1000000000000000000L;
#ifdef __DEBUG

/**
 * For DEBUG
 * https://github.com/ta7uw/cpp-pyprint
 */
#include "cpp-pyprint/pyprint.h"

#endif

void Main() {
    int Q;
    cin >> Q;
    while (Q--) {
        string X, Y;
        cin >> X >> Y;
        ll N = X.size();
        ll M = Y.size();
        vector<vector<ll>> dp(N + 1, vector<ll>(M + 1, 0));
        rep(i, N) {
            rep(j, M) {
                if (X[i] == Y[j]) {
                    dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + 1);
                }
                dp[i + 1][j + 1] = max({dp[i + 1][j + 1], dp[i][j + 1], dp[i + 1][j]});
            }
        }
        cout << dp[N][M] << '\n';
    }
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    Main();
    return 0;
}