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<bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < n; i++)
#define pb push_back
using namespace std;
typedef long long ll;

int main(){
  int n;
  cin>>n;
  
  rep(i,n){  
    string a,b;
    cin>>a>>b;
    
    int dp[1005][1005];
    rep(i,1005)rep(j,1005)dp[i][j] = 0;
    
    rep(j,a.size())rep(k,b.size()){
      if(a[j]==b[k]) dp[j+1][k+1] = max(dp[j+1][k+1],dp[j][k]+1);
      else dp[j+1][k+1] = max(max(dp[j][k+1],dp[j+1][k]),dp[j+1][k+1]);
    }
    
    cout << dp[a.size()][b.size()] << endl;
  }
}

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

typedef pair<int,int> P;
typedef long long ll;

#define rep(i,n) for(int i=1;i<=n;i++)
#define pb push_back 
#define inf INT_MAX/4 
#define ALL(v) v.begin(),v.end()
#define N 1001

int c[N][N];

int lcs(string X, string Y){
  int lx = X.size();
  int ly = Y.size();
  int ans = 0;

  X = ' ' + X;
  Y = ' ' + Y;

  rep(i,lx) rep(j,ly) c[i][j] = 0;

  rep(i,lx){
   rep(j,ly){
    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]);
    }
    ans = max(ans, c[i][j]);
   }
  }

  return ans;
}

int main(void){

  int q;

  cin >> q;

  while(q--){
    string X, Y;
    cin >> X >> Y;

    cout << lcs(X, Y) << endl;
  
  }

  return 0;
}