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 <string>
#include <vector>
#include <algorithm>

constexpr int nil = -1;

class ILcs
{
public:
    using vvi = std::vector<std::vector<int>>;
    virtual int lcs() = 0;
    virtual int lcs(int i1, int i2) = 0;
};

class LcsLoop : public ILcs
{
public:

    LcsLoop(std::string str1, std::string str2)
        : str1 {" " + str1}
        , str2 {" " + str2}
        , dp {vvi(str1.size() + 1, std::vector<int>(str2.size() + 1))}
    {
        CalcLcs();
    }

    int lcs() override
    {
        return lcs(str1.size() - 1, str2.size() - 1);
    }

    int lcs(int i1, int i2) override
    {
        return dp[i1][i2];
    }

private:

    std::string str1;
    std::string str2;
    vvi         dp;
    
    void CalcLcs()
    {
        for (int i = 0; i < str1.size(); ++i)
            dp[i][0] = 0;
        for (int i = 0; i < str2.size(); ++i)
            dp[0][i] = 0;

        for (int i = 1; i < str1.size(); ++i)
        {
            for (int j = 1; j < str2.size(); ++j)
            {
                if (str1[i] == str2[j])
                    dp[i][j] = dp[i - 1][j - 1] + 1;
                else
                    dp[i][j] = std::max(dp[i][j - 1], dp[i - 1][j]);
            }
        }
    }
};

//class LcsReccursion : public ILcs
//{
//public:
//    LcsReccursion(const std::string& str1, const std::string& str2)
//        : str1 {str1}
//        , str2 {str2}
//        , dp {vvi(str1.size(), std::vector<int>(str2.size(), nil))}
//    {}
//
//    int lcs() override
//    {
//        return lcs(str1.size() - 1, str2.size() - 1);
//    }
//
//    int lcs(int i1, int i2) override
//    {
//        if (dp[i1][i2] != nil)
//            return dp[i1][i2];
//
//        if (i1 == 0 || i2 == 0)
//        {
//            if (i1 == 0 && i2 == 0) return dp[i1][i2] = (str1[i1] == str2[i2]);
//            else if (i1 == 0)       return dp[i1][i2] = std::max(lcs(i1, i2 - 1), (str1[i1] == str2[i2] ? 1 : 0));
//            else                    return dp[i1][i2] = std::max(lcs(i1 - 1, i2), (str1[i1] == str2[i2] ? 1 : 0));
//        }
//
//        dp[i1][i2] = std::max(lcs(i1 - 1, i2), lcs(i1, i2 - 1))
//            + (str1[i1] == str2[i2]);
//        return dp[i1][i2];
//    }
//
//private:
//
//    std::string str1;
//    std::string str2;
//    vvi         dp;
//};

void solve()
{
    using namespace std;

    int n;
    cin >> n;

    string s1, s2;

    for (int i = 0; i < n; ++i)
    {
        cin >> s1 >> s2;
        LcsLoop lcs {s1, s2};
        //LcsReccursion lcs {s1, s2};
        cout << lcs.lcs() << ((i != n - 1) ? "\n" : "");
    }
}

int main()
{
    solve();
    return 0;
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int dp[1001][1001];
string s,t;
int n,m,a,ans;
int main(){
  cin>>a;
  for(int b=0;b<a;b++){
    cin>>s>>t;
    for(int i=0;i<=1000;i++)
      for(int j=0;j<=1000;j++)
	dp[i][j]=0;
    m=s.size();
    n=t.size();
    ans=0;
    for(int i=1;i<=m;i++){
      for(int j=1;j<=n;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[m][n]<<endl;
  }
  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;
  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(){
  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 <algorithm>

using namespace std;

int main() {
  int Tc; cin >> Tc;
  
  while(Tc--) {
    string s, t; cin >> s >> t;
    
    int dp[1001][1001] = {{}};
    
    int const N = s.size(), M = t.size();
    
    for(int i=0; i<N; i++) {
      for(int j=0; j<M; j++) {
        if(s[i] == t[j]) {
          dp[i+1][j+1] = dp[i][j] + 1;
        }
        else {
          dp[i+1][j+1] = max(dp[i][j+1], dp[i+1][j]);
        }
      }
    }
    
    cout << dp[N][M] << endl;
  }
  
  return 0;
}

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

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

template<class T>
bool chmax(T &a, const T &b) {
    if(a<b) {
        a=b;
        return false;
    }
    return true;
}

using namespace std;

int dp[1003][1003];
int main() {
    int q; cin>>q;
    rep(_,q) {
        memset(dp,0,sizeof(dp));
        string s,t;
        cin>>s>>t;
        s=" "+s;
        t=" "+t;
        rep(i,s.size()){
            rep(j,t.size()) {
                if(i&&j) {
                    if(s[i]==t[j]) dp[i][j]=dp[i-1][j-1]+1;
                    else {
                        chmax(dp[i][j],dp[i-1][j]);
                        chmax(dp[i][j],dp[i][j-1]);
                    }
                }
            }
            //rep(j,t.size()) cout<<dp[i][j]<<" ";
            //cout<<endl;
        }
        int ans=0;

        rep(i,s.size()) chmax(ans,*max_element(dp[i],dp[i]+t.size()));
        cout<<ans<<endl;
    }

    return 0;
}