Go: package main

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

const (
	initialBufSize = 100000
	maxBufSize     = 1000000
)

var sc *bufio.Scanner

func initScanner(r io.Reader) *bufio.Scanner {
	buf := make([]byte, initialBufSize)

	sc := bufio.NewScanner(r)
	sc.Buffer(buf, maxBufSize)
	sc.Split(bufio.ScanWords) // bufio.ScanLines
	return sc
}

func main() {
	sc = initScanner(os.Stdin)
	resolve()
}

func resolve() {
	n := scanInt(sc)
	results := []int{}
	for i := 0; i < n; i++ {
		results = append(results, resolveInstance())
	}
	for _, v := range results {
		fmt.Println(v)
	}
	return
}

func resolveInstance() int {
	x, y := scanString(sc), scanString(sc)
	lx, ly := len(x), len(y)
	dp := make([][]int, lx+1)
	dp[0] = make([]int, ly+1)
	for i := 1; i <= lx; i++ {
		dp[i] = make([]int, ly+1)
		dp[i][0] = dp[i-1][0]
		for j := 1; j <= ly; j++ {
			dp[i][j] = dp[i-1][j]
			if dp[i][j] < dp[i][j-1] {
				dp[i][j] = dp[i][j-1]
			}
			if x[i-1] == y[j-1] {
				cL := dp[i-1][j-1] + 1
				if dp[i][j] < cL {
					dp[i][j] = cL
				}
			}
		}
	}
	return dp[lx][ly]
}

const (
	remove = 0 + iota
	match
)

// snip-scan-funcs
func scanInt(sc *bufio.Scanner) int {
	sc.Scan()
	i, _ := strconv.Atoi(sc.Text())
	return int(i)
}
func scanString(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

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;
}

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

using namespace std;

typedef long long ll;

#define FOR(index, init, max) for (int index = (init); index < (max); i++)
#define REP(index, max) for (int index = 0; index < (max); i++)
#define FOREACH(x, array) for (auto&& (x) : array)
#define VECCIN(vec) for (auto&& vec_i : vec) cin >> vec_i
#define VECCOUT(vec) for (const auto& vec_i : vec) cout << vec_i << endl

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

    int dp[1001][1001] = {0};

    while(q > 0) {
        string x, y;
        cin >> x >> y;

        for (int x_i = 0; x_i < x.length(); x_i++) {
            for (int y_i = 0; y_i < y.length(); y_i++) {
                if (x[x_i] == y[y_i]) {
                    dp[x_i + 1][y_i + 1] = dp[x_i][y_i] + 1;
                }
                else {
                    dp[x_i + 1][y_i + 1] = max(dp[x_i][y_i + 1], dp[x_i + 1][y_i]);
                }
            }
        }

        cout << dp[x.length()][y.length()] << endl;
        q--;
    }

    return 0;
}

C++: 
#include <iostream>
#include <stdio.h>
#include <string>
#include <string.h>
#define MAX 1001

using namespace std;

int LCS(char *X, char *Y)
{
    int m = strlen(X);
    int n = strlen(Y);
    int  c[MAX][MAX] = {0};
    for (int i = 0; i <= m; i++)
    {
        c[0][i] = 0;
    }
    for (int j = 0; j <= n; j++)
    {
        c[j][0] = 0;
    }

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

    return c[m][n];
}

int main(int argc, char *argv[])
{
    char X[MAX], Y[MAX];
    int q;
    scanf("%d", &q);
    for (int i = 0; i < q; i++)
    {
        scanf("%s", X);
        scanf("%s", Y);
        printf("%d\n", LCS(X, Y));
    }
    return 0;
}

C++: #include <iostream> 
#include <cstring> 
using namespace std;
int c[1001][1001];

int lcs(string x, string y)
{
    int maxl = 0;
    int m = x.length(), n = y.length();
 
    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][j-1], c[i-1][j]);
            }
            maxl = max(maxl, c[i][j]);
        } 
    } 
    return maxl;
}

int main()
{
    string x,y;
    int q;
    cin>>q;
    while(q--)
    {
        cin>>x>>y;
        int ans = lcs(x, y);
        cout<<ans<<endl;
    }
    return 0;
}