Go: package main

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

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// if S[i-1] == T[j-1] {
				// 	dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				// } else {
				// 	dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				// }
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

C++: #include<iostream>
#include<cstdio>
#include<cstring>
#define _A_ true
using namespace std;
 
int main(){
  int n,AC=0,strA,strB;
  int dp[1010][1010];
  char *A = new char[1500];
  char *B = new char[1500];
 
  scanf("%d",&n);
  while(_A_){
    if(AC == n)break;
    scanf("%s",A);
    scanf("%s",B);
    for(int i=0;i<1010;i++)for(int j=0;j<1010;j++)dp[i][j]=0;
strA = strlen(A); 
strB = strlen(B);

    for(int i=0;i<strA;i++){
      for(int j=0;j<strB;j++){
    if(A[i] == B[j]){
      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];
      }
    }
      }
    }
    printf("%d\n",dp[strA][strB]);
    AC++;
  }
  delete [] A;
  delete [] B;
 
  return 0;
}

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;
}