Go: package main

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

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}
	for i := 0; i < n; i++ {
		strX := nextText(sc)
		strY := nextText(sc)
		fmt.Println(calcLcs(strX, strY))
	}
}

func calcLcs(strX, strY string) int {
	lenX, lenY := len(strX), len(strY)
	memo := make([][]int, lenX+1)
	for i := 0; i < lenX+1; i++ {
		memo[i] = make([]int, lenY+1)
	}

	lcs := 0
	for i := 1; i < lenX+1; i++ {
		for j := 1; j < lenY+1; j++ {
			if strX[i-1] == strY[j-1] {
				memo[i][j] = memo[i-1][j-1] + 1
			} else {
				if memo[i-1][j] > memo[i][j-1] {
					memo[i][j] = memo[i-1][j]
				} else {
					memo[i][j] = memo[i][j-1]
				}
			}
			if memo[i][j] > lcs {
				lcs = memo[i][j]
			}
		}
	}
	return lcs
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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

#define int             long long
#define FOR( i, m, n )  for( int (i) = (m); (i) < (n); (i)++ )
#define REP( i, n )     FOR( i, 0, n )
#define REPR( i, m )    for( int (i) = (m); (i) >= 0; (i)-- )
#define REPONE( i, n )  FOR( i, 1, n + 1 )
#define ALL( a )        (a).begin(), (a).end()
#define MP              make_pair

using namespace std;
using P = pair<int, int>;

template<class T>bool chmax( T& a, const T& b ) { if( a < b ) { a = b; return 1; } return 0; }
template<class T>bool chmin( T& a, const T& b ) { if( a > b ) { a = b; return 1; } return 0; }

const int INF = 1e9;
const int MOD = 1e9 + 7;

int dp[1001][1001];

signed main(){
    int N; cin >> N;
    REP( i, N ){
        string s, t; cin >> s >> t;
        REP( i, s.size() ){
            REP( j, t.size() ){
                if( s[i] == t[j] ){
                    dp[i + 1][j + 1] = dp[i][j] + 1;
                }else{
                    dp[i + 1][j + 1] = max( dp[i + 1][j], dp[i][j + 1] );
                }
            }
        }

        cout << dp[s.size()][t.size()] << endl;
    }
}

C++: #include <stdio.h>
#include <vector>
#include <list>
#include <map>
#include <array>
#include <memory>
#include <string>
#include <iostream>
#include <sstream>
#include <algorithm>
#include <cmath>
#include <unordered_map>
#include <stdexcept>


using std::string;
using std::vector;


//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// util
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

std::vector<std::string> split(const std::string& input, char delimiter)
{
    std::istringstream stream(input);

    std::string field;
    std::vector<std::string> result;
    while (std::getline(stream, field, delimiter)) {
        result.push_back(field);
    }
    return result;
}



//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// user func
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void printList(const vector<int>& list) {
    // print
    for(int i = 0; i < list.size(); i++){
        printf(" %d", list[i]);
    }
    printf("\n");
}



//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// logic
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

// Longest Common Subsequence
int LCS(const string& x, const string& y) {
    int result = 0;
    vector<vector<int>> table(x.length() + 1, vector<int>(y.length() + 1, 0));
    
    for (int i = 1; i <= x.length(); i++) {
        for (int j = 1; j <= y.length(); j++) {
            if (x[i-1] == y[j-1]) {
                table[i][j] += table[i-1][j-1] + 1;
            } else {
                table[i][j] = std::max(table[i-1][j], table[i][j-1]);
            }
            result = std::max(result, table[i][j]);
        }
    }
    return result;
}

void solve() {
    int n;
    scanf("%d", &n);
    for(int i = 0; i < n; i++){
        char bufX[1024];
        char bufY[1024];
        scanf("%s", bufX);
        scanf("%s", bufY);
        printf("%d\n", LCS(string(bufX), string(bufY)));
    }
}


//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// main
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
int main() {
    solve();
    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 <string>
#include <vector>
using namespace std;

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

  for(int i=0; i<q; i++){
    string x, y;
    cin >> x >> y;
    
    int nx, ny;
    nx = x.size();
    ny = y.size();
    
    vector< vector<int> > lcs(nx+1, vector<int>(ny+1, 0));

    for(int i=1; i<=nx; i++){
      for(int j=1; j<=ny; j++){
	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 <iostream>
#include <string>
#define repi(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,a) repi(i,0,a)
#define clr(a,v) memset((a),(v),sizeof(a))

int q;
int dp[1000][1000];
std::string s, t;

int rec( int i, int j )
{
  int &ret = dp[i][j];

  if( ~ret )
    return ret;

  if( i == s.size() || j == t.size() )
    return 0;

  ret = 0;

  if( s[i] == t[j] )
    ret = std::max( ret, rec( i+1, j+1 )+1 );

  ret = std::max( ret, std::max( rec( i+1, j ), rec( i, j+1 ) ) );

  return ret;
}

int main()
{
  scanf( "%d", &q );
  while( q-- )
  {
    std::cin >> s >> t;

    clr( dp, -1 );

    std::cout << rec( 0, 0 ) << std::endl;
  }

  return 0;
}

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



auto lcs(const std::string& a, const std::string& b, std::vector<std::vector<int> >*tp) {
	auto tab = *tp;

	for (auto&e : tab) {
		std::fill(std::begin(e),std::end(e),0);
	}

	for (decltype(a.size()) ai{1}; ai <= a.size();++ai) {
		for (decltype(ai) bi{1}; bi<=b.size(); ++bi) {
			if (a[ai-1] == b[bi-1])
				tab[ai][bi] = tab[ai - 1][bi - 1] + 1;
			else
				tab[ai][bi] = std::max(tab[ai - 1][bi], tab[ai][bi - 1]);
		}
	}
	return tab[a.size()][b.size()];
}

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

	std::vector<std::vector<int>> buf{};
	buf.resize(1005);
	for (auto&e : buf)
		e.resize(1005);

	for (int i{}; i < q; ++i) {
		std::string x, y;
		std::cin >> x >> y;
		std::cout << lcs(x, y, &buf)<<"\n";
	}

	return 0;
}