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++: /*
 * Problem Description: Longest Common Subsequence
 * Category: Dynamic Programming
 * Author: Khan
 * Date: 18th October, 2017
 */

#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

static const int N = 10000;

int lcs(string x, string y)
{
    int c[N + 1][N + 1];
    int m = x.size();
    int n = y.size();
    int maxLength = 0;
    x = ' ' + x;
    y = ' ' + y;
    for (int i = 1; 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]);
            maxLength = max(maxLength, c[i][j]);
        }
    }
    return maxLength;
}

int main(int argc, char const *argv[])
{
    //freopen("sample.txt", "r", stdin);
    string x, y;
    int n;
    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        cin >> x >> y;
        cout << lcs(x, y) << endl;
    }
    return 0;
}

C++: #include <limits.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <algorithm>
#include <cassert>
#include <cfloat>
#include <complex>
#include <functional>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

using namespace std;

#define chmax(x, y) x = max(x, y)
#define chmin(x, y) x = min(x, y)
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define Sort(v) sort(v.begin(), v.end())
#define Reverse(v) reverse(v.begin(), v.end())
#define Lower_bound(v, x) \
  distance(v.begin(), lower_bound(v.begin(), v.end(), x))
#define Upper_bound(v, x) \
  distance(v.begin(), upper_bound(v.begin(), v.end(), x))

using ll = long long;
using ull = unsigned long long;
using P = pair<ll, ll>;
using T = tuple<ll, ll, ll>;
using vll = vector<ll>;
using vP = vector<P>;
using vT = vector<T>;
using vvll = vector<vector<ll>>;
using vvP = vector<vector<P>>;
using dqll = deque<ll>;

ll dx[9] = {-1, 1, 0, 0, -1, -1, 1, 1, 0};
ll dy[9] = {0, 0, -1, 1, -1, 1, -1, 1, 0};

const ll INF = 1LL << 50;

const ll mod = 1e9 + 7;

int main() {
  ll q;
  cin >> q;
  rep(i_q, q) {
    string s, t;
    cin >> s >> t;
    ll ns = (ll)s.size(), nt = (ll)t.size();
    vvll dp(ns + 1, vll(nt + 1, 0));
    rep(i, ns) rep(j, nt) {
      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]);
      }
    } // j, i
    cout << dp[ns][nt] << endl;
  }  // q

  return 0;
}

C++: //#include "aizu.h"
#include <iostream>
#include <string>
#include <vector>

//namespace alds1_10_c{
template<class T>
T myMin(const T& arg){
	return arg;
}
template<class F, class... S>
F myMin(const F& first, const S&... second){
	F m = myMin(second...);
	if (m > first){
		return first;
	}else{
		return m;
	}
}
int f(std::string::iterator str1, const std::string& str2, const std::vector<int>& vec){
	std::vector<int> new_v;
	new_v.push_back(vec[0] + 1);
	{
		auto v = vec.begin() + 1;
		for (auto i = str2.begin(); i != str2.end(); ++i, ++v){
			if (*i == *str1){
				new_v.push_back(myMin(*v, *(v - 1), new_v.back()));
			}else{
				new_v.push_back(myMin(*v + 1, new_v.back() + 1));
			}
		}
	}
	if (*(++str1) != '\0'){
		return f(str1, str2, new_v);
	}else{
		return new_v.back();
	}
}
int main(){
	int n;
	std::cin >> n;
	for (int i = 0; i < n; ++i){
		std::string str1, str2;
		std::cin >> str1 >> str2;
		std::vector<int> vec;
    vec.push_back(0);
		for (int j = 0; j < str2.size(); ++j){
			vec.push_back(j);
		}
		std::cout << (str1.size() + str2.size() - f(str1.begin(), str2, vec)) / 2 << "\n";
	}
}
//}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#define NIL -1
using namespace std;

int count(const string& X, int i, const string Y, int j,
          vector<vector<int> >& MEMO){
    if (i >= X.size() || j >= Y.size()) return 0;
    if (MEMO[i][j] != NIL) return MEMO[i][j];
    int j_tmp = j;
    int saiyou = 0;
    while (j_tmp < Y.size()) {
        if (X[i] == Y[j_tmp]) {
            saiyou = count(X, i + 1, Y, j_tmp + 1, MEMO) + 1;
            break;
        };
        j_tmp++;
    }
    int next_X = count(X, i + 1, Y, j    , MEMO);
    // int next_Y = count(X, i    , Y, j + 1, MEMO);
    return MEMO[i][j] = max(saiyou, next_X);
}

int main(){
    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        string X, Y;
        cin >> X >> Y;
        vector<vector<int> > MEMO(X.size(), vector<int>(Y.size(), NIL));
        cout << count(X, 0, Y, 0, MEMO) << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<string>
using namespace std;
string x,y;
int dp[1005][1005];
int lcs(string x,string y)
{

    int Max=-1;
    int n=x.size(),m=y.size();
    x=' '+x;
    y=' '+y;
    for(int i=1;i<=n;i++)dp[i][0]=0;        //边界条件就是从此开始的，所以要置为1，
    for(int i=1;i<=m;i++)dp[0][i]=0;        //不然循环查询的次数多了就会造成错误
    for(int i=1;i<=n;i++)
        for(int j=1;j<=m;j++)
        {
         if(x[i]==y[j])dp[i][j]=dp[i-1][j-1]+1;
         else dp[i][j]=max(dp[i-1][j],dp[i][j-1]);
         //Max=max(Max,dp[i][j]);
        }
    return dp[n][m];
}
int main()
{
    int n;
    cin>>n;
    for(int i=0;i<n;i++)
    {
         cin>>x>>y;
        cout<<lcs(x,y)<<endl;
    }
    return 0;
}