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 <cstdio>
#include <string>

using namespace std;

string a,b;

int lcs(int i,int j){
  if(i==0 || j==0) return 0;
  if(a[i]==b[j]){
    return lcs(i-1,j-1)+1;
  }else{
    return max(lcs(i,j-1),lcs(i-1,j));
  }
}

int main(){
  int n; cin>>n;
  for(int i=0;i<n;i++){
    cin>>a>>b;
    a = ' ' + a;
    b = ' ' + b;
    cout<<lcs(a.size()-1,b.size()-1)<<endl;
  }
}

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 <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;
}