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] = 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>
using namespace std;

#define FOR( i, m, n )  for( int (i) = (m); (i) < (n); (i)++ )
#define REP( i, n )     FOR( i, 0, n )
#define ALL( a )        (a).begin(), (a).end()             

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

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

	int maxl;

	string s1, s2;
	REP( i, n ) {
		cin >> s1 >> s2;
		s1 = ' ' + s1;
		s2 = ' ' + s2;
		maxl = 0;
		memset( dp, 0, sizeof( int ) );
		FOR( j, 1, s1.size() ) {
			FOR( k, 1, s2.size() ) {
				if( s1[j] == s2[k] ) {
					dp[j][k] = dp[j - 1][k - 1] + 1;
				} else {
					dp[j][k] = max( dp[j - 1][k], dp[j][k - 1] );
				}
				maxl = max( dp[j][k], maxl );
			}
		}

		cout << maxl << endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, s, e) for (int i = (int)(s); i <= (int)(e); i++)
#define printYesNo(is_ok) puts(is_ok ? "Yes" : "No");
#define SORT(v) sort(v.begin(), v.end());
#define RSORT(v) sort(v.rbegin(), v.rend());
#define REVERSE(v) reverse(v.begin(), v.end());

template <typename T>
void printlnVector(T v)
{
  rep(i, v.size())
  {
    cout << v[i] << endl;
  }
}

template <typename T>
void printVector(T v)
{
  rep(i, v.size())
  {
    cout << v[i] << " ";
  }
  cout << endl;
}

int main()
{
  int q;
  cin >> q;
  rep(Q, q)
  {
    string X, Y;
    cin >> X >> Y;
    vector<vector<int> > dp(X.size(), vector<int>(Y.size()));
    if(X[0]  == Y[0])
      dp[0][0]++;

    rep(i, X.size() - 1)
    {
      if(X[i + 1] == Y[0])
        dp[i + 1][0]++;
      dp[i + 1][0] = max(dp[i + 1][0], dp[i][0]);
    }

    rep(i, Y.size() - 1)
    {
      if(X[0] == Y[i + 1])
        dp[0][i + 1]++;
      dp[0][i + 1] = max(dp[0][i + 1], dp[0][i]);
    }

    rep(i, X.size() - 1) rep(j, Y.size() - 1)
    {
      if(X[i + 1] == Y[j + 1])
        dp[i + 1][j + 1] = dp[i][j] + 1;
      else
        dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1]);
    }

    cout << dp[X.size() - 1][Y.size() - 1] << endl;
  }
  return 0;
}

C++: #include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<iostream>
using namespace std;

#define N_MAX 1000

char X[N_MAX];
char Y[N_MAX];
char LCS[N_MAX][N_MAX];


int longest(int x, int y)
{
    for (int i = 0; i < x+1; i++) {
        for (int j = 0; j < y+1; j++) {
            if (i == 0 || j == 0) {
                LCS[i][j] = 0;
//                printf("0 LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
            else if (X[i-1] == Y[j-1]) {
                LCS[i][j] = LCS[i-1][j-1] + 1;
//                printf("1 LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
            else {
                LCS[i][j] = (LCS[i-1][j] > LCS[i][j-1]) ? LCS[i-1][j] : LCS[i][j-1]; 
//                printf("LCS[%d][%d] = %d\n", i, j, LCS[i][j]);
            }
        }
    }

    return LCS[x][y]; 
}

int main() {
    int q;
    int x;
    int y;

    cin >> q;

    for (int i = 0; i < q; i++) {
        scanf("%s", X);
        x = strlen(X);
        scanf("%s", Y);
        y = strlen(Y);
        cout << longest(x, y) << endl;
    }
        
    return 0;
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for (int i=0; i<(int)(n); i++)
#define all(v) v.begin(), v.end()
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
const ll MOD = 1000000007;
const ll INF = 9999999999;
const int INFI = 2147483647;
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;}
template<class T> inline T powerM(T a,T b){if (b==0) return 1;
  T tmp = powerM(a,b/2); if (b%2==0) return tmp*tmp%MOD; else return tmp*tmp%MOD*a%MOD; }

int main() {
  int q; cin >>q;
  vector<vector<int>> dp;
  rep(query, q){
    string s,t; cin >>s >>t;
    int n = s.size(), m = t.size();
    dp.assign(n+1, vector<int>(m+1, 0));
    // dp[i][j]...sのi文字目まで、tのj文字目までの最長共通部分列の長さ
    for (int i=0; i<n; i++){
      for (int j=0; j<m; j++){
        if (s.at(i) == t.at(j)) chmax(dp[i+1][j+1], dp[i][j] + 1);
        chmax(dp[i+1][j+1], dp[i][j+1]);
        chmax(dp[i+1][j+1], dp[i+1][j]);
      }
    }
    cout <<dp[n][m] <<endl;
  }
}

C++: #include <iostream>
#include <list>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <algorithm>
#include <cmath>
#include <string>
using namespace std;
typedef long long lli;
typedef vector<lli> vll;
typedef vector<bool> vbl;
typedef vector<vector<lli> > mat;
typedef vector<vector<bool> > matb;
typedef vector<string> vst;
typedef pair<lli,lli> pll;
typedef pair<double,double> pdd;

lli n;
string x;
string y;

mat dp;

int main(){
    cin >> n;
    for(lli i = 0;i < n;i++){
        cin >> x >> y;
        dp = mat(x.size()+2,vll(y.size()+2));
        for(lli i = 0;i <= x.size();i++){
            for(lli j = 0;j <= y.size();j++){
                dp[i+1][j] = max(dp[i+1][j],dp[i][j]);
                dp[i][j+1] = max(dp[i][j+1],dp[i][j]);
                if(x[i] == y[j]) dp[i+1][j+1] = max(dp[i+1][j+1],dp[i][j]+1);
            }
        }
        cout << dp[x.size()][y.size()] << endl;
    }
    return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
static const int N=1001;
int lcs(string& X,string& Y){
  int c[N][N] = {};
  int m=X.size();
  int n=Y.size();

  int max1=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]);
      }
      max1=max(max1,c[i][j]);
    }
  }
  return max1;
}

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;
}