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<string>
#include<algorithm>
using namespace std;

int main(){
    int N;
    cin>>N;
    if(N>20){
        for(int i=0;i<N;i++){
            string inp1,inp2;
            cin>>inp1;
            cin>>inp2;
            int dp[101][101]={};
            for(int j=1;j<=inp1.size();j++){
                for(int k=1;k<=inp2.size();k++){
                    if(inp1[j]==inp2[k]){
                        dp[j][k]=dp[j-1][k-1]+1;
                    }else{
                        dp[j][k]=max(dp[j-1][k],dp[j][k-1]);
                    }
                }
            }
            cout<<dp[inp1.size()][inp2.size()]<<endl;
        }
    }else{
        for(int i=0;i<N;i++){
            string inp1,inp2;
            cin>>inp1;
            cin>>inp2;
            int dp[1001][1001]={};
            for(int j=1;j<=inp1.size();j++){
                for(int k=1;k<=inp2.size();k++){
                    if(inp1[j]==inp2[k]){
                        dp[j][k]=dp[j-1][k-1]+1;
                    }else{
                        dp[j][k]=max(dp[j-1][k],dp[j][k-1]);
                    }
                }
            }
            cout<<dp[inp1.size()][inp2.size()]<<endl;
        }
    }
    
    return 0;
}

C++: #include<cstdio>
#include<iostream>
#include<string>
#include<algorithm>
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 maxcost=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]);
      }
      maxcost=max(maxcost,c[i][j]);
    }
  }
  return maxcost;
}

int main(){
  string s1,s2;
  int n;
  scanf("%d",&n);
  for(int i=0;i<n;i++){
    cin >> s1 >> s2;
    printf("%d\n",lcs(s1,s2));
  }
  return 0;
}

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

constexpr int MAX_XY = 1000;

int lx, ly, q, dp[MAX_XY][MAX_XY];
std::string sx, sy;

void fill_dp(){
    for(int i = 1; i <= lx; ++i){
        for(int j = 1; j <= ly; ++j){
            if(sx[i - 1] == sy[j - 1]) dp[i][j] = dp[i - 1][j - 1] + 1;
            else dp[i][j] = std::max(dp[i - 1][j], dp[i][j - 1]);
        }
    }
}

void solve(){
    fill_dp();
    std::cout << dp[lx][ly] << std::endl;
    return;
}

int main(){
    std::cin >> q;
    
    for(int i = 0; i < q; ++i){
        std::cin >> sx >> sy;
        lx = sx.size(), ly = sy.size();
        solve();
    }
    return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
#define len_max 1000


string X;
string Y;
int dp[len_max+1][len_max+1];

int lcs(){
    int m = X.length();
    int n = Y.length();

    X = ' ' + X;//ずらす
    Y = ' ' + Y;
    

    for(int i = 0; i <= n; i++){
        dp[i][0] = 0;
    }

    for(int i = 0; i <= m; i++){
        dp[0][i] = 0;
    }

    for(int i = 1; i <= n; i++){
        for(int j = 1; j <= m; j++){
            if(Y[i] == X[j]){
                dp[i][j] = dp[i-1][j-1] + 1;
            }
            else{
                dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
            }
        }
    }
    return dp[n][m];

}


int main(){
    int q;
    cin >> q;

    int ans[q];

    for(int i = 0; i < q; i++){
        cin >> X >> Y;
        //printf("%d\n", lcs());
        ans[i] = lcs();
    }

    for(int i = 0; i < q; i++){
        printf("%d\n", ans[i]);
    }

    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
const int MAXL = 1e3+7;
char s1[MAXL];
char s2[MAXL];
int dp[MAXL][MAXL];
int maxLCS(char s1[], char s2[]){
    int l1 = strlen(s1);
    int l2 = strlen(s2);
    int i;
    for(i = 0; i <= l1; i++){
        dp[0][i] = 0;
    }
    for(i = 0; i <= l2; i++){
        dp[i][0] = 0;
    }
    int j;
    for(i = 1; i <= l2; i++){
        for(j = 1; j <= l1; j++){
            int max_k = max(dp[i-1][j], dp[i][j-1]);
            if(s1[j-1] == s2[i-1]) max_k = max(max_k, dp[i-1][j-1]+1);
            else max_k = max(max_k, dp[i-1][j-1]);
            dp[i][j]= max_k;
        }
    }
    return dp[l2][l1];
}
int main(){
//    freopen(".../in.txt", "r", stdin);
    int q;
    scanf("%d", &q);
    for(int i = 0; i < q; i++){
        scanf("%s", s1);
        scanf("%s", s2);
        int q = maxLCS(s1, s2);
        printf("%d\n", q);
    }
    return 0;
}

C++: #include <iostream>
#include <stdio.h>
#include <string>
#include <cmath>

#define MAX_LENGTH 1000
#define NIL -1
using namespace std;
//think easy make easy

int q;//num of datasets
string X;
string Y;
char map[MAX_LENGTH+1][MAX_LENGTH+1];

int findMaxLength(int x,int y){//x:Xの終端.y:Yの終端(0オリジン)
	int val;

	if(x < 0 || y < 0) return 0;

	if(map[x][y] == NIL){
		if(X.at(x) == Y.at(y)){
			val = findMaxLength(x-1,y-1) +1;
		}else{
			val = max(findMaxLength(x-1,y),findMaxLength(x,y-1));
		}
		map[x][y] = val;//メモ
		return val;
	}else return map[x][y];
}

int main(){
	
	scanf("%d",&q);

	for(int i=0;i<q;i++){
		cin >>X; cin >> Y;
		for(int i=0;i<X.size();i++){
			for(int j=0;j<Y.size();j++){
				map[i][j] = NIL;
			}
		}
	
		cout <<findMaxLength(X.size()-1,Y.size()-1) <<endl;
	}

	return 0;
}