Go: package main

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

// I/O
type Scanner struct {
	sc *bufio.Scanner
}

func NewScanner() *Scanner {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	sc.Buffer(make([]byte, 1024), int(1e+9))
	return &Scanner{sc}
}

func (s *Scanner) nextStr() string {
	s.sc.Scan()
	return s.sc.Text()
}

func (s *Scanner) nextInt() int {
	i, e := strconv.Atoi(s.nextStr())
	if e != nil {
		panic(e)
	}
	return i
}

func (s *Scanner) nextFloat() float64 {
	f, e := strconv.ParseFloat(s.nextStr(), 64)
	if e != nil {
		panic(e)
	}
	return f
}

func (s *Scanner) nextRuneSlice() []rune {
	return []rune(s.nextStr())
}

func (s *Scanner) nextIntSlice(n int) []int {
	res := make([]int, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextInt()
	}
	return res
}

func (s *Scanner) nextFloatSlice(n int) []float64 {
	res := make([]float64, n)
	for i := 0; i < n; i++ {
		res[i] = s.nextFloat()
	}
	return res
}

// Arithmetic
func max(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m < i {
			m = i
		}
	}
	return m
}

func min(nums ...int) int {
	m := nums[0]
	for _, i := range nums {
		if m > i {
			m = i
		}
	}
	return m
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

func pow(x, y int) int {
	res := 1
	for i := 0; i < y; i++ {
		res *= x
	}
	return res
}

func ceil(a, b int) int {
	if a%b == 0 {
		return a / b
	} else {
		return a/b + 1
	}
}

// Sort
type RuneSlice []rune

func (a RuneSlice) Len() int           { return len(a) }
func (a RuneSlice) Less(i, j int) bool { return a[i] < a[j] }
func (a RuneSlice) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }

// Main
func main() {
	sc := NewScanner()
	wtr := bufio.NewWriter(os.Stdout)
	Q := sc.nextInt()
	for q := 0; q < Q; q++ {
		X, Y := sc.nextStr(), sc.nextStr()
		xLen, yLen := len(X), len(Y)
		dp := make([][]int, xLen+1)
		for i := 0; i <= xLen; i++ {
			dp[i] = make([]int, yLen+1)
		}
		for x := 0; x <= xLen; x++ {
			for y := 0; y <= yLen; y++ {
				if x == 0 || y == 0 {
					dp[x][y] = 0
				} else if X[x-1] == Y[y-1] {
					dp[x][y] = dp[x-1][y-1] + 1
				} else {
					dp[x][y] = max(dp[x-1][y], dp[x][y-1])
				}
			}
		}
		fmt.Fprintln(wtr, dp[xLen][yLen])
	}

	wtr.Flush()
}

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

int main(){
    int q;
    cin >> q;
    while(q-- > 0){
        string s, t;
        cin >> s >> t;
        s = " " + s; // padding
        t = " " + t; // padding
        int h = s.length(), w = t.length();
        vector<vector<int>> dp(h, vector<int>(w,0));
        for(int i = 1; i < h; i++){
            for(int j = 1; j < w; j++){
                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
                if(s[i] == t[j])    dp[i][j] = max(dp[i][j], dp[i-1][j-1]+1);
            }
        }
        cout << dp[h-1][w-1] << endl;
    }
    return 0;
}

C++: #include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<iostream>
using namespace std;
#define MAX 1000

int main(){
  int n;
  cin>>n;
  string a,b;
  for(int i=0;i<n;i++){
    cin>>a>>b;
    int C[MAX+1][MAX+1]={0};
    for(int i=1;i<=a.size();i++){
      for(int j=1;j<=b.size();j++){
        if(a[i]==b[j]) C[i][j]=C[i-1][j-1]+1;
        else{
          C[i][j]=max(C[i-1][j],C[i][j-1]);
        }
      }
    }
    cout<<C[a.size()][b.size()]<<endl;
  }
  
}

C++: //最长公共子序列 
#include<iostream>
#include<algorithm>
#include<string>
using namespace std;

int LCS(string s1,string s2)
{
	int c[1005][1005];
	int m1=s1.length();
		int m2=s2.length();
		int maxx=0;
		s1=' '+s1;
		s2=' '+s2;
		for(int i=1;i<=m1;i++)
			c[i][0]=0;
		for(int j=1;j<=m2;j++)
			c[0][j]=0;
		int i,j;
		for(i=1;i<=m1;i++)
		{
			for(j=1;j<=m2;j++)
			{
				if(s1[i]==s2[j])
					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];
				}
				maxx=max(maxx,c[i][j]);
			}
			
		}
		return maxx;	
	
}
int main()
{
	int n;
	cin>>n;
	
	while(n--)
	{
		string s1,s2;	
		cin>>s1>>s2;
		cout<<LCS(s1,s2)<<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 = 0; 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 x, y;
    int n;
    cin >> n;
    for(int i = 0; i < n; i++) {
        cin >> x >> y;
        cout << lcs(x, y) << 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=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;
}

C++: #include <bits/stdc++.h>
using namespace std;

int main(){
    int n;
    cin >> n;
    vector<string> S(2*n);
    for (auto i = 0; i < 2*n; i++)
    {
        string s;
        cin >> s;
        S[i] = s;
    }

    for (auto i = 0; i < 2*n; i += 2)
    {
        string x = S[i];
        string y = S[i + 1];
        int sizex = x.size();
        int sizey = y.size();

        vector<vector<int>> m(sizex+1, vector<int>(sizey+1));

        for (auto j = 0; j < sizex+1; j++)
        {                
                m[j][0] = 0;   
        }

        for (auto j = 0; j < sizey+1; j++)
        {
                m[0][j] = 0;
        }


        for (auto j = 1; j < sizex+1; j++)
        {
            for (auto k = 1; k < sizey+1; k++)
            {
                if(x[j-1] == y[k-1]){
                    m[j][k] = m[j - 1][k - 1] + 1;
                }else{
                    m[j][k] = max(m[j - 1][k], m[j][k - 1]);
                }
            }
        }

        cout << m[sizex][sizey] << endl;

    }   
    
}

C++: #include <bits/stdc++.h>
using namespace std;
static const int N=1000;

int lsc(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 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]==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 << lsc(s1,s2) << endl;
    }
    return 0;
}