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<iostream>
#include<string>
#include<algorithm>
using namespace std;

static const int N = 1000;

int lcs(string X,string Y){
    int c[N+1][N+1];
    int m = X.size();
    int n = Y.size();
    int maxl = 0;
    X = ' ' + X;
    Y = ' ' + Y;
    for(int i=1; i<=m; i++) c[i][0]=0;
    for(int j=0; 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]);
            }
            maxl = max(maxl, c[i][j]);
        }
    }
    
    return maxl;
}

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;
}

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

string X;
string Y;

int calc(int x, int y){
    if (X[x] == '\0') return 0;
    if (y == string::npos) return 0;

    int unuse = calc(x + 1, y);
    int use = 0;
    int y_target = Y.find(X[x], y);
    if (y_target == string::npos) {
        use = 0;
    } else {
        use = calc(x + 1, y_target + 1) + 1;
    }
    return max(unuse, use);
}

int main(){
    int q;
    cin >> q;
    for (int i = 0; i < q; i++) {
        cin >> X;
        cin >> Y;
        cout << calc(0, 0) << endl;
    }

    return 0;
}

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

int N,len1,len2;
string seq1,seq2;
int dp[1000+10][1000+10];

int main() {
	cin >> N;
	for (int M=0; M<N; M++){
		cin >> seq1 >> seq2;
		len1 = seq1.length();
		len2 = seq2.length();
		for (int i=1; i<=len1; i++){
			for (int j=1; j<=len2; j++){
				if (seq1[i-1] == seq2[j-1]){
					dp[i][j] = dp[i-1][j-1] + 1;
				}else if (dp[i][j-1] > dp[i-1][j]){
					dp[i][j] = dp[i][j-1];
				}else{
					dp[i][j] = dp[i-1][j];
				}
			}
		}
		cout << dp[len1][len2] << endl;
	}
	
	return 0;
}

C++: //	created : 16/03/15
// 	author   : Rp7rf
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <set>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define rep(i,a) for(int i = 0 ; i < a ; i ++)
#define loop(i,a,b) for(int i = a ; i < b ; i ++)
#define vi vector<int>
#define mp make_pair
#define pb push_back
#define MOD 1000000007
#define INF 1e9


int main(void){
	int n;
	string s1,s2;
	cin>>n;
	int dp[1010][1010];
	rep(i,n){
		int ret = 0;
		cin>>s1>>s2;
		rep(i,s1.size())dp[i][0] = 0;
		rep(j,s2.size())dp[0][j] = 0;

		loop(i,0,s1.size()){
			loop(j,0,s2.size()){
				if(s1[i] == s2[j]){
					dp[i][j] = dp[i-1][j-1] + 1;
				}else{
					dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
				}
				ret = max(ret,dp[i][j]);
			}
		}
		cout<<ret<<endl;
	}
}

C++: #include <bits/stdc++.h>
#include <math.h>

using namespace std;

long long inf=1000000007;

long long modpow(long long n,long long p,long long mod);

int main(){
	long long n;
	cin>>n;
	for(long long i=0;i<n;i++){
		string s,t;
		cin>>s>>t;
		long long ss=s.size(),ts=t.size();
		vector<vector<long long>> dp(ss+1,vector<long long>(ts+1,-1));
		dp.at(0).at(0)=0;

		for(long long j=0;j<=ss;j++){
			for(long long k=0;k<=ts;k++){
				if(j==0 || k==0){
					dp.at(j).at(k)=0;
					continue;
				}

				if(s.at(j-1)==t.at(k-1)){
					dp.at(j).at(k)=dp.at(j-1).at(k-1)+1;
				}else{
					dp.at(j).at(k)=max(dp.at(j-1).at(k),dp.at(j).at(k-1));
				}
			}
		}

		cout<<dp.at(ss).at(ts)<<endl;
	}

	return 0;
}

long long modpow(long long n,long long p,long long mod){
	if(p==0) return 1;
	if(p%2==0) return (modpow(n,p/2,mod)*modpow(n,p/2,mod))%mod;
	if(p%2==1) return (modpow(n,p-1,mod)*n)%mod;
	cerr<<"ERROR"<<endl;
	return 1;
}

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

using namespace std;

//L[i][j] X[0]..X[i]??¨X[0]..Y[j]???LCS
int L[1001][1001]={};
int main(){
  int testnum;
  cin>>testnum;
  for(int t=0;t<testnum;++t){
    string X,Y;
    cin>>X>>Y;

    for(int i=1;i<=X.length();++i){
      for(int j=1;j<=Y.length();++j){
        if(X[i-1]==Y[j-1])
          L[i][j] = 1 + L[i-1][j-1];
        else
          L[i][j] = max(L[i][j-1],L[i-1][j]);
      }
    }

    cout << L[X.length()][Y.length()] << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

#define rep(i,x) for(int i=0;i<x;++i)
#define rrep(i,x) for(int i=x-1;i>=0;--i)

int dp[1010][1010];

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

    rep(_, q) {
        memset(dp, -1, sizeof(dp));
        dp[0][0] = 0;

        string a,b; cin >> a>>b;

        int n = a.size(), m = b.size();
        rep(i, n+1) {
            rep(j, m+1) {
                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 (a[i] == b[j]) {
                    dp[i + 1][j + 1] = max(dp[i + 1][j + 1], dp[i][j] + 1);
                }
            }
        }

        cout << dp[n][m] << endl;
    }
}