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"
using namespace std;
typedef long long ll;
// #define int long long

template <class T>
bool INRANGE(T x, T a, T b) { return a <= x && x <= b; }
template <class T>
inline bool chmin(T &a, T b)
{
    if (a > b)
    {
        a = b;
        return true;
    }
    return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
    if (a < b)
    {
        a = b;
        return true;
    }
    return false;
}

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RREP(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define RFOR(i, a, b) for (int i = (a); i >= (b); --i)
#define ALL(v) (v).begin(), (v).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" \
                      << " " << __FILE__ << endl;

typedef vector<int> vi;
typedef vector<string> vs;
typedef vector<vi> vvi;
typedef pair<int, int> pii;

vvi dp;
string gx, gy;
int dfs(int ix, int iy) {
    if (ix == gx.length() or iy == gy.length()) {
        return 0;
    }
    if (dp[ix][iy] != -1) return dp[ix][iy];

    if (gx[ix] != gy[iy]) {
        int c1 = dfs(ix+1, iy);
        int c2 = dfs(ix, iy+1);
        dp[ix][iy] = max(c1, c2);
    } else {
        int c1 = dfs(ix+1, iy+1)+1;
        int c2 = dfs(ix, iy+1);
        dp[ix][iy] = max(c1, c2);
    }

    return dp[ix][iy];
}

void solve(string x, string y) {
    gx = x, gy = y;
    dp = vvi(1005, vi(1000, -1));
    cout << dfs(0, 0) << endl;
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n;
    cin >> n;
    REP(i, n) {
        string x, y;
        cin >> x >> y;
        solve(x, y);
    }

    return 0;
}

C++: /*
 * c.cc: 
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>

using namespace std;

/* constant */

const int MAX_N = 1000;

/* typedef */

/* global variables */

int dp[MAX_N + 1][MAX_N + 1];

/* subroutines */

/* main */

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

  while (qn--) {
    string x, y;
    cin >> x >> y;

    int xn = x.size(), yn = y.size();

    memset(dp, 0, sizeof(dp));

    for (int i = 0; i <= xn; i++)
      for (int j = 0; j <= yn; j++) {
	if (i < xn && j < yn && x[i] == y[j] &&
	    dp[i + 1][j + 1] < dp[i][j] + 1)
	  dp[i + 1][j + 1] = dp[i][j] + 1;

	if (i < xn && dp[i + 1][j] < dp[i][j])
	  dp[i + 1][j] = dp[i][j];

	if (j < yn && dp[i][j + 1] < dp[i][j])
	  dp[i][j + 1] = dp[i][j];
      }

    printf("%d\n", dp[xn][yn]);
  }

  return 0;
}

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

using namespace std;

int lcs (string x, string y) {

    int m, n, c[1001][1001], i, j, maxl = 0;

    m = x.size();
    n = y.size();

    x = ' ' + x;
    y= ' ' + y;

    for (i = 0; i <= m; i++) {
        c[i][0] = 0;
    }
    for (j = 1; j <= n; j++) {
        c[0][j] = 0;
    }

    for (i = 1; i <= m; i++) {
            for (j = 1; j <= n; j++) {

                if (x[i - 1] == y[j - 1]) {
                    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 () {

    int N, i;
    string x, y;

    cin >> N;

    for (i = 0; i < n; i++) {
        cin >> x >> y;
        cout << lcs (x, y) << endl;

    }

    return 0;

}

C++: #include <bits/stdc++.h>
using namespace std;

int main(){
  int n;
  int dp[1111][1111];
  cin >> n;
  while(n--){
    string str1, str2;
    cin >> str1 >> str2;
    memset(dp,0,sizeof(dp));
    for(int i = 1; i <= str1.size(); i++){
      for(int j = 1; j <= str2.size(); j++){
        if(str1[i-1] == str2[j-1]){
          dp[i][j] = dp[i-1][j-1] + 1;
        }else dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
      }
    }
    cout<<dp[str1.size()][str2.size()]<<endl;
  }
  return 0;
}