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<algorithm>
#include<string>

int main(){
    int q;
    std::string X,Y;
    std::cin>>q;

    int xy[1000][1000]={};
    
    for(int i=0;i<q;i++){
        std::cin>>X>>Y;
        //int xy[1001][1001]={};
        for(int j=1;j<=X.size();j++){
            for(int k=1;k<=Y.size();k++){
                if(X[j-1]==Y[k-1]){
                    xy[j][k]=xy[j-1][k-1]+1;
                }else{
                    xy[j][k]=std::max(xy[j][k-1],xy[j-1][k]);
                }
            }
        }
        std::cout<<xy[X.size()][Y.size()]<<"\n";
    }

return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <set>
#include <algorithm>
#include <array>
#include <complex>
#include <utility>
#include <map>
#include <inttypes.h>

int LCS(std::string s,std::string t){
    int n,m,c[n+1][m+1];
    n=s.size();
    m=t.size();
    int maxlen=0;
    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(s[i]==t[i]){
                c[i][j]=c[i-1][j-1]+1;
            }else{
                c[i][j]=std::max(c[i-1][j],c[i][j-1]);
            }
            maxlen=std::max(c[i][j],maxlen);
        }
    }
    return maxlen;
}
int main(){
	int N;
    
    std::cin >> N;
    std::string s1,s2;
    for(int i=0;i<N;i++){
        std::cin >> s1 >> s2;
        std::cout << LCS(s1,s2) <<std::endl;
    }
        
    
    return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int q;
  cin >> q;
  while (q--) {
    string x, y;
    cin >> x >> y;
    int m = x.length();
    int n = y.length();
    vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
    for (int i = 1; i <= m; i++) {
      for (int j = 1; j <= n; j++) {
        if (x[i - 1] == y[j - 1]) {
          dp[i][j] = dp[i - 1][j - 1] + 1;
        } else {
          dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
      }
    }
    int ret = dp[m][n];
    cout << ret << '\n';
  }
  return 0;
}

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

#define REP(i, n) for(int (i) = 0; (i) < (n); (i)++)

string str1, str2;
int dp[1001][1001];
int k;

int solve(int i, int j)
{
  if(dp[i][j] > 0)
    return dp[i][j];
  if(i >= str1.size() || j >= str2.size()){
    if(i < str1.size()){
      return solve(i + 1, k);
    }else{
      return 0;
    }
  }
  if(str1[i] == str2[j]){
    k = j + 1;
    int n, m = 0;
    for(int l = i + 1; l < str1.size(); l++){
      n = solve(l, j + 1);
      m = (n > m) ? n : m;
    }
    dp[i][j] = m + 1;
    return dp[i][j];
  }else{
    return solve(i, j + 1);
  }
}
  
int main()
{
  int q, n, ans = 0;
  cin >> q;
  cin.ignore();
  REP(i, q){
    getline(cin, str1);
    getline(cin, str2);
    if(str1.size() < str2.size())
      swap(str1, str2);
    fill(&dp[0][0], &dp[1001][0], -1);
    for(int j = str1.size() - 1; j >= 0; j--){
      n = solve(j, 0);
      ans = (n > ans) ? n : ans;
    }
    cout << ans << endl;
    ans = 0;
  }
}

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

int main(){
  
  int q, lcs[1010][1010] = {};
  string a, b;

  //input
  cin >> q;
  for(int i = 0;i < q;i++){
    cin >> a;
    cin >> b;

    for(int r = 0;r < (int)a.size();r++){
      for(int c = 0;c < (int)b.size();c++){
	//if a_i = b_j, chain a_i to LCS of a_{i-1} and b_{j-1}
        if(a[r] == b[c]) lcs[r + 1][c + 1] = lcs[r][c] + 1;
	//else LCS of a_{i-1} and b_j or a_i and b_{j-1}
        else lcs[r + 1][c + 1] = max(lcs[r + 1][c], lcs[r][c + 1]);
      }
    }
    
    //output
    cout << lcs[a.size()][b.size()] << endl;
  }
  
  return 0;
}

C++: // http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_10_C
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <vector>

#define debug(x) cout << #x << "==" << x << endl;

using namespace std;

//??\???
#define MAX_LEN 1000
int N;
int dp[MAX_LEN + 1][MAX_LEN + 1];

void print_dp_table(int n, int m) {
  for(int i = 0; i < n; i++) {
    for(int j = 0; j < m; j++) {
      cout <<setw(2) << dp[i][j];
    }
    cout << "\n";
  }
  cout << "\n";
}

int main() {
  ios::sync_with_stdio(false);

  cin >> N;

  string s1, s2;

  while( cin >> s1 >> s2 ) {

    std::vector<char> a;
    std::vector<char> b;
    for(char& c : s1) {
      a.push_back(c);
    }
    for(char& c : s2) {
      b.push_back(c);
    }


    // dp ????????????????????????
    fill(dp[0], dp[MAX_LEN + 1], 0);

    for( int i = 0; i < (int)a.size(); i++) {
      for( int j = 0; j < (int)b.size(); j++) {
        if( a[i] == b[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]);
        }
      }
    }

    // print_dp_table(a.size(), b.size());
    cout << dp[a.size()][b.size()] << endl;

  }

  return 0;
}

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

int dp[1005][1005];
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int lcs(string &x, string &y) {
    memset(dp, 0, sizeof(dp));
    int xn = x.size();
    int yn = y.size();
    rep(i, xn) {
        rep(j, yn) {
            if (x[i] == y[j])
                dp[i + 1][j + 1] = max(dp[i][j] + 1, max(dp[i][j + 1], dp[i + 1][j]));
            else
                dp[i + 1][j + 1] = max(dp[i][j], max(dp[i][j + 1], dp[i + 1][j]));
        }
    }
    return dp[xn][yn];
}

int main() {
    int n;
    cin >> n;
    rep(i, n) {
        string x, y;
        cin >> x >> y;
        int ans = lcs(x, y);
        cout << ans << endl;
    }
}