Go: package main

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

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func main() {
	fp := os.Stdin
	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(os.Stdout)

	n := getNextInt(scanner)
	for i := 0; i < n; i++ {
		x := getNextString(scanner)
		y := getNextString(scanner)

		fmt.Fprintln(writer, lcs(x, y))
	}

	writer.Flush()
}

func lcs(x, y string) int {
	lx := len(x)
	ly := len(y)
	dp := make([][]int, lx+1)
	for i := 0; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
	}
	for i := 0; i < lx; i++ {
		for ii := 0; ii < ly; ii++ {
			if x[i] == y[ii] {
				dp[i+1][ii+1] = dp[i][ii] + 1
				continue
			}
			dp[i+1][ii+1] = dp[i][ii+1]
			if dp[i+1][ii] > dp[i+1][ii+1] {
				dp[i+1][ii+1] = dp[i+1][ii]
			}
		}
	}
	return dp[lx][ly]
}

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;  // X[0] に空白を挿入
  Y = ' ' + Y;  // Y[0] に空白を挿入
  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 <cstring>
#include <algorithm>
using namespace std;

#define N 1000

int main(void) {
    int n;
    cin >> n;
    
    for(int k = 0; k < n; ++k) {
        string s1, s2; 
        int max = -1;
        int ans[N + 1][N + 1];
        
        cin >> s1 >> s2;
        
        for(int i = 0; i < s1.length(); ++i) {
            ans[i][0] = 0;
        }
        for(int j = 0; j < s2.length(); ++j) {
            ans[0][j] = 0;
        }
        
        for(int i = 0; i < s1.length(); ++i) {
            for(int j = 0; j < s2.length(); ++j) {
                if(s1[i] == s2[j]) {
                    ans[i + 1][j + 1] = ans[i][j] + 1;
                } else {
                    ans[i + 1][j + 1] = (ans[i][j + 1] > ans[i + 1][j]) ? ans[i][j + 1] : ans[i + 1][j];
                }
                max = (max > ans[i + 1][j + 1]) ? max : ans[i + 1][j + 1];
            }
        }
        
        cout << max << endl;
    }
}

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

int dp[1001][1001];

int main(){
  int q,xl,yl;
  char X[1001],Y[1001];

  cin >> q;

  for (int i=0;i<q;i++){
    cin >> X >> Y;

    xl=strlen(X);
    yl=strlen(Y);
  
    for (int i=1;i<=xl;i++)dp[0][i]=0;
    for (int i=1;i<=yl;i++)dp[i][0]=0;
    for (int i=0;i<yl;i++)
      for (int j=0;j<xl;j++){
	if (X[j]==Y[i]){
	  dp[i+1][j+1]=dp[i][j]+1;
	}else{
	  if (dp[i+1][j]>dp[i][j+1])
	    dp[i+1][j+1]=dp[i+1][j];
	  else
	    dp[i+1][j+1]=dp[i][j+1];	    
	}
      }
    cout << dp[yl][xl]<<endl;
    
  }
  
  return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <string>
#define INF 100000

using namespace std;

int dp[1000][1000];
string X, Y;

int lcs(int i,int j){
  if(i < 0 || j < 0) return 0;
  if(dp[i][j] != INF) return dp[i][j];

  if(X[i] == Y[j]){
    dp[i][j] = lcs(i-1, j-1) + 1;
    return dp[i][j];
  } else {
    dp[i][j] =  max(lcs(i-1,j), lcs(i, j-1));
    return dp[i][j];
  }
}

void clear(){
  for(int i = 0;i < X.size();i++){
    for(int j = 0;j < Y.size();j++){
      dp[i][j] = INF;
    }
  }
}

int main(){
  int q;

  cin >> q;

  for(int i = 0;i < q;i++){
    cin >> X >> Y;
    
    clear();
    
    cout << lcs(X.size()-1, Y.size()-1) << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repr(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, m, n) for (int i = (m); i < (n); ++i)
#define FORR(i, m, n) for (int i = (m); i >= (n); --i)
using namespace std;
typedef long long ll;
const ll mod = 1000000007;
const ll mod2 = 998244353;
const int INF = 1000000005;
const int MAX = 1005;

int lcs[MAX][MAX];

int main() {
  int q, nx, ny;
  string x, y;
  cin >> q;

  rep(i, q) {
    cin >> x >> y;
    nx = x.size();
    ny = y.size();

    rep(i, nx+1) {
      rep(j, ny+1) {
        lcs[i][j] = 0;
      }
    }

    FOR(i, 1, nx+1) {
      FOR(j, 1, ny+1) {
        if (x[i-1] == y[j-1]) {
          lcs[i][j] = lcs[i-1][j-1] + 1;
        }
        else {
          lcs[i][j] = max(lcs[i-1][j], lcs[i][j-1]);
        }
      }
    }

    cout << lcs[nx][ny] << endl;
  }

  
  return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

using ll = long long;
using P = pair<ll, ll>;
using Graph = vector<vector<ll>>;
#define rep(i, n) for(ll i=0;i<(ll)(n);i++)
#define rep2(i, m, n) for(ll i=m;i<(ll)(n);i++)
#define rrep(i, n, m) for(ll i=n;i>=(ll)(m);i--)
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
const int ddx[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[8] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll MOD = 1000000007;
const ll INF = 1000000000000000000L;
#ifdef __DEBUG

/**
 * For DEBUG
 * https://github.com/ta7uw/cpp-pyprint
 */
#include "cpp-pyprint/pyprint.h"

#endif

void Main() {
    int Q;
    cin >> Q;
    while (Q--) {
        string X, Y;
        cin >> X >> Y;
        ll N = X.size();
        ll M = Y.size();
        vector<vector<ll>> dp(N + 1, vector<ll>(M + 1, 0));
        rep(i, N) {
            rep(j, M) {
                if (X[i] == Y[j]) {
                    dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + 1);
                }
                dp[i + 1][j + 1] = max({dp[i + 1][j + 1], dp[i][j + 1], dp[i + 1][j]});
            }
        }
        cout << dp[N][M] << '\n';
    }
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    Main();
    return 0;
}

C++: 
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
char len1[1001], len2[1001];
 
LCS(int x, int y){
  int i,j,c[1001][1001];
 
   for(i=0;i<=x;i++){
      c[i][0]=0;
  }
 
  for(j=0;j<=y;j++){
    c[0][j]=0;
  }
 
  for(i=1;i<=x;i++){
    for(j=1;j<=y;j++){
      if(len1[i-1]==len2[j-1]){
    c[i][j]=c[i-1][j-1]+1;
      }else if(c[i-1][j-1]>=c[i][j-1]){
    c[i][j] = c[i-1][j];
      }else{
    c[i][j] = c[i][j-1];
      }
    }
  }
 
  if(i==0 || j==0){
    return 0;
  }else if(i>0 && j>0 && x == y){
    return c[i-1][j-1];
  }else if(i>0 && j>0 && x!=y){
    return c[x][y];
  }
}
 
main(){
  int n,i,l1,l2,result;
 
  scanf("%d", &n);
   
  for(i=0;i<n;i++){
    scanf("%s",len1);
    scanf("%s",len2);
    l1=strlen(len1);
    l2=strlen(len2);
    
    result=LCS(l1,l2);
    printf("%d\n",result);
  }
  return 0;
}