Go: package main

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

// define
var (
	sc = bufio.NewScanner(os.Stdin)
)

func bordersInt(in_map [][]int, invalid int) [][]int{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]int, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]int, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func bordersString(in_map [][]string, invalid string) [][]string{
	H, W := len(in_map), len(in_map[0])
	out_map := make([][]string, H+2)
	for h:=0; h<H+2; h++ {
		out_map[h] = make([]string, W+2)
		for w:=0; w<W+2; w++ {
			out_map[h][w] = invalid
		}
	}
	for h:=0; h<H; h++{
		for w:=0; w<W; w++{
			out_map[h+1][w+1] = in_map[h][w] 
		}
	}
	return out_map
}

func scanIntLine(len int) []int{
	arr := make([]int, len)
	for i:=0; i<len; i++{
		sc.Scan()
		tmp, err := strconv.Atoi(sc.Text())
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func scanStringLine(len int) []string{
	arr := make([]string, len)
	for i:=0; i<len; i++{
		sc.Scan()
		arr[i] = sc.Text()
	}
	return arr
}

func scanIntSplit(len int) []int{
	arr := make([]int, len)
	sc.Scan()
	for i, v := range strings.Split(sc.Text(), " "){
		tmp, err := strconv.Atoi(v)
		if err == nil{
			arr[i] = tmp
		}
	}
	return arr
}

func maxInt(args... int) int{
	sort.Ints(args)
	return args[len(args)-1]
}

func main(){
	buf := make([]byte, 0)
    sc.Buffer(buf, 1000000009)
	var n int 
	fmt.Scan(&n)
	dp := make([][]int, 1003)
	for i:=0; i<1003; i++ {
		dp[i] = make([]int, 1003)
	}
	input_lines := scanStringLine(2*n)
	for i:=0; i<n; i++ {
		S, T := input_lines[2*i], input_lines[2*i+1]
		lenS, lenT := len(S), len(T)
		for i:=1; i<lenS+1; i++ {
			for j:=1; j<lenT+1; j++ {
				if S[i-1] == T[j-1] {
					dp[i][j] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// if S[i-1] == T[j-1] {
				// 	dp[i][j] = maxInt(dp[i-1][j-1]+1, dp[i-1][j], dp[i][j-1])
				// } else {
				// 	dp[i][j] = maxInt(dp[i-1][j], dp[i][j-1])
				// }
			}
		}
		fmt.Println(dp[lenS][lenT])
	}
}

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;
}