Go: package main

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

func max(x, y int) int {
	if x < y {
		return y
	} else {
		return x
	}
}

/*********************************************************************
長さmの列X_(m)と長さnの列Y_(n)の最長共通部分列LCSは、
	(1)X[m] == Y[n]ならば、X_(m-1)とY_(n-1)のLCSにX[m]を繋げたもの
	(2)X[m] != Y[n]ならば、X_(m-1)とY_(n)のLCSもしくはX_(m)とY_(n-1)のLCS
	のいずれかのうち長い方

c[m+1][n+1]：c[i][j]にX_(i)とY_(j)のLCSの長さを格納する二次元配列
*********************************************************************/

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Scan()
	n, _ := strconv.Atoi(scanner.Text())
	for i := 0; i < n; i++ {
		scanner.Scan()
		s1 := scanner.Text()
		scanner.Scan()
		s2 := scanner.Text()
		s1, s2 = s1 + " ", s2 + " "
		c := make([][]int, len(s1))
		for i := range c {
			c[i] = make([]int, len(s2))
		}

		LCS := 0

		for i := 1; i < len(s1); i++ {
			for j := 1; j < len(s2); j++ {
				if s1[i] == s2[j] {
					c[i][j] = c[i-1][j-1] + 1
				} else {
					c[i][j] = max(c[i-1][j], c[i][j-1])
				}
				LCS = max(LCS, c[i][j])
			}
		}
		fmt.Println(LCS)
	}
}

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



int lcs(string x, string y){

  int m = x.length();
  int n = y.length();

  int c[m + 1][n + 1];

  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(x[i - 1] == y[j - 1]){
        c[i][j] = c[i - 1][j - 1] + 1;
      }
      else if(c[i - 1][j] > c[i][j - 1]){
        c[i][j] = c[i - 1][j];
      }
      else{
        c[i][j] = c[i][j - 1];
      }
    }

  }

  return c[m][n];
}

int main(){

  int q;

  string x, y;

  cin >> q;

  for(int i = 0; i < q; i++){
    cin >> x;
    cin >> y;
    cout << lcs(x, y) << endl;
  }



  return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i,a,n) for(int i=a;i<n;i++)
#define repr(i,a,n) for(int i=a;i>=n;i--)
#define INF 999999999
#define pb(a) push_back(a)

using namespace std;
typedef pair<int, int> pii;
typedef long long int ll;
typedef vector<pii> VP;

int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0};

int main() {
    int num; cin >> num;
    rep(k,0,num) {
        string s1,s2;
        cin >> s1 >> s2;

        int dp[1001][1001]; //s1???i??????????????§???s2???j??????????????§??§???LCS????±???????????????????
        int n = s1.length();
        int m = s2.length();
        rep(i,0,m+1) dp[0][i] = 0;

        rep(i,0,n) {
            rep(j,0,m) {
                if(s1[i]==s2[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<bits/stdc++.h>
using namespace std;
typedef long long int ll;

int main() {
	ios::sync_with_stdio(false); cin.tie(0);

	int N; cin >> N;
	string s[310];
	for (int i = 0; i < 2*N; i+=2) {
		cin >> s[i] >> s[i + 1];
	}
	for (int l = 0; l < 2 * N; l += 2) {
		int dp[1010][1010];
		int m = 0;
		int i = 0;
		while (i < s[l].length()&&s[l][i]!=s[l+1][0]) {
			dp[i][0] = 0;
			i++;
		}
		while (i < s[l].length()) {
			dp[i][0] = 1;
			i++;
			m = 1;
		}
		i = 0;
		while (i < s[l+1].length() && s[l+1][i] != s[l][0]) {
			dp[0][i] = 0;
			i++;
		}
		while (i < s[l+1].length()) {
			dp[0][i] = 1;
			i++;
			m = 1;
		}
		for (i = 1; i < s[l].length(); i++) {
			for (int j = 1; j < s[l + 1].length(); j++) {
				dp[i][j] = dp[i - 1][j - 1];
				if (s[l][i] == s[l + 1][j])dp[i][j]++;
				dp[i][j] = max({ dp[i][j],dp[i][j - 1],dp[i - 1][j] });
				m = max(dp[i][j], m);
			}
		}
		cout << m << endl;
	}
}

C++: #include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int dp[1002][1002];

int main(){
	int n;cin >> n;
	string x, y;
	while(n--){
		cin >> x >> y;
		for(int i = 1;i <= x.size();i++){
			for(int j = 1;j <= y.size();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]);
			}
		}
		cout << dp[x.size()][y.size()] << endl;
	}
	return 0;
}

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() << endl;
    }
}

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

C++: #include<string>
#include<iostream>

using namespace std;

#define 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=1;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;
}