Go: package main

/*
最長共通部分列
*/

import (
	"bufio"
	"bytes"
	"fmt"
	"log"
	"os"
	"strconv"
	"strings"
)

func larger(l, r int) int {
	if l > r {
		return l
	}
	return r
}

var memo [1001][1001]int

func countLCS(x, y string) int {
	x = " " + x
	y = " " + y
	max := 0
	for xi := 1; xi < len(x); xi++ {
		for yi := 1; yi < len(y); yi++ {
			if x[xi] == y[yi] {
				memo[xi][yi] = memo[xi-1][yi-1] + 1
			} else {
				memo[xi][yi] = larger(memo[xi-1][yi], memo[xi][yi-1])
			}
			max = larger(max, memo[xi][yi])
		}
	}
	return max
}

func main() {
	scanner := makeScanner(1024)
	q := eGetInt(scanner)
	for i := 0; i < q; i++ {
		x := eGetLine(scanner)
		y := eGetLine(scanner)
		fmt.Println(countLCS(x, y))
	}
}

////////////////////////////////////////////////////////////////////////////////
// ライブラリ
////////////////////////////////////////////////////////////////////////////////
func makeScanner(maxByte int) *bufio.Scanner {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Buffer(make([]uint8, 0, 8192), maxByte)
	return scanner
}
func makeWordScanner() *bufio.Scanner {
	scanner := makeScanner(8192)
	scanner.Split(bufio.ScanWords)
	return scanner
}
func eGetLine(r *bufio.Scanner) string {
	if r.Scan() {
		return r.Text()
	}
	err := r.Err()
	if err != nil {
		log.Fatal(err)
	}
	// EOF
	return ""
}
func eGetInt(r *bufio.Scanner) int {
	line := eGetLine(r)
	return eAtoi(line)
}
func eGetFields(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Fields(line)
}
func eGetInts(r *bufio.Scanner) []int {
	fields := eGetFields(r)
	ints := make([]int, len(fields))
	for i := 0; i < len(ints); i++ {
		ints[i] = eAtoi(fields[i])
	}
	return ints
}
func eGetChars(r *bufio.Scanner) []string {
	line := eGetLine(r)
	return strings.Split(line, "")
}
func eAtoi(s string) int {
	n, err := strconv.Atoi(s)
	if err != nil {
		log.Fatal(err)
	}
	return n
}

type ints []int

func (s ints) String() string {
	var buf bytes.Buffer
	buf.WriteString("[")
	sep := ""
	for _, v := range s {
		buf.WriteString(fmt.Sprintf("%s%d", sep, v))
		sep = ", "
	}
	buf.WriteString("]")
	return buf.String()
}

func reverse(a ints) ints {
	r := make(ints, len(a))
	for i := 0; i < len(a); i++ {
		r[i] = a[len(a)-1-i]
	}
	return r
}
func max(a ints) (int, bool) {
	if len(a) == 0 {
		return 0, false
	}
	m := a[0]
	for _, e := range a {
		if e > m {
			m = e
		}
	}
	return m, true
}
func min(a []int) int {
	m := a[0]
	for _, v := range a {
		if v < m {
			m = v
		}
	}
	return m
}

func sum(a ints) int {
	if len(a) == 0 {
		return 0
	}
	sum := 0
	for _, e := range a {
		sum += e
	}
	return sum
}
func find(n int, a ints) int {
	for i, v := range a {
		if n == v {
			return i
		}
	}
	return -1
}

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;
}