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;
using ll=long long;
using vb=vector<bool>;
using vvb=vector<vb>;
using vd=vector<double>;
using vvd=vector<vd>;
using vi=vector<int>;
using vvi=vector<vi>;
using vl=vector<ll>;
using vvl=vector<vl>;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll>;
using vs=vector<string>;
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define rep(i,n) range(i,0,n)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define range(i,a,n) for(int i=(a);i<(n);i++)

#define LINF    	((ll)1ll<<60)
#define INF     	((int)1<<30)
#define EPS     	(1e-9)
#define MOD     	(1000000007ll)
#define fcout(a)	cout<<setprecision(a)<<fixed
#define fs 			first
#define sc			second
#define PI			3.1415926535897932384

int dx[]={1,0,-1,0,1,-1,-1,1},dy[]={0,1,0,-1,1,1,-1,-1};
template<class S,class T>ostream&operator<<(ostream&os,pair<S,T>p){os<<"["<<p.first<<", "<<p.second<<"]";return os;};
template<class S>auto&operator<<(ostream&os,vector<S>t){bool a=1; for(auto s:t){os<<(a?"":" ")<<s; a=0;} return os;}
void OUT(bool b){cout<<(b?"YES":"NO")<<endl;}
void Out(bool b){cout<<(b?"Yes":"No")<<endl;}
void out(bool b){cout<<(b?"yes":"no")<<endl;}
int popcnt(int x) { return __builtin_popcount(x); }
int popcnt(ll x) { return __builtin_popcountll(x); }
int clz(int x) { return 31 - __builtin_clz(x); }
int clz(ll x) { return 63 - __builtin_clzll(x); }
int ctz(int x) { return __builtin_ctz(x); }
int ctz(ll x) { return __builtin_ctzll(x); }

class compare {
public:
	bool operator()(tuple<ll, ll> a, tuple<ll, ll> b) {
		return (get<1>(a) > get<1>(b));
	}
};

void solve(){
	string a,b;
	cin>>a>>b;
	vvi dp(a.size()+1,vi(b.size()+1));
	rep(i,a.size()){
		rep(j,b.size()){
			if(a[i]==b[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]);
		}
	}
	cout<<dp[a.size()][b.size()]<<endl;
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	int n;
	cin>>n;
	rep(i,n)solve();
}

C++: 

#include<iostream>
#include<cstdlib>

int main(){
  int n;
  std::string x,y;
  std::cin>>n;
  int a[1000][1000];
  int b[n];

  for(int i=0;i<n;i++){
    std::cin>>x;
    std::cin>>y;
    for(int j=0;j<1000;j++){
      for(int k=0;k<1000;k++){
	a[j][k]=0;
      }
    }
    for(int j=0;j<x.size();j++){
      for(int k=0;k<y.size();k++){
	if(x[j]==y[k]){
	  a[j][k]=a[j-1][k-1]+1;
	}else{
	  if(a[j-1][k]>a[j][k-1]){
	    a[j][k]=a[j-1][k];
	  }else{
	    a[j][k]=a[j][k-1];
	  }
	}
      }
    }
    b[i]=a[x.size()-1][y.size()-1];
  }

  for(int i=0;i<n;i++){
  std::cout<<b[i]<<"\n";
  }

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i, a, b) for (int i = (a); i < (int)(b); ++i)
#define rrep(i, a, b) for (int i = (int)(b) - 1; i >= (int)(a); --i)
#define all(c) c.begin(),c.end()
#define sz(x) ((int)x.size())
using pii = pair<int, int>;
using vvi = vector<vector<int>>;
using vi  = vector<int>;
constexpr int INF = 1001001001001001001LL;
/*
<NAME> 最長共通部分列 (Longest Common Subsequence)
<TRIGGER> LCS
<TAG> DP, etc
<*NOTE>
文字列の最長共通部分列を求める。$O(NM)$
<*CODE> */
int lcs(string a, string b) {
    int n = sz(a), m = sz(b);
    vvi dp(n + 1, vi(m + 1, 0));
    rep(i, 0, n) {
        rep(j, 0, m) {
            if (a[i] == b[j]) {
                dp[i + 1][j + 1] = dp[i][j] + 1;
            } else {
                dp[i + 1][j + 1] = max(dp[i][j + 1], dp[i + 1][j]);
            }
        }
    }
    return dp[n][m];
}

// hash : [59, 176, 206, 65, 188, 72, 103, 19]]

signed main() {
    int Q;
    cin >> Q;
    while (Q--) {
        string S, T;
        cin >> S >> T;
        cout << lcs(S, T) << endl;
    }
}

C++: #include<iostream>
#include<string>
#include<algorithm>
using namespace std;
#define MAX 1000
int dp[MAX + 1][MAX + 1];
int LCS(string STR1, string STR2)
{
	int length1 = STR1.size();
	int length2 = STR2.size();
	//???????????¨????????????????????????
	STR1 = ' ' + STR1;
	STR2 = ' ' + STR2;
	for (int i = 0; i < length1; i++)
	{
		for (int l = 0; l < length2; l++)dp[i][l] = 0;
	}
	for (int i = 1; i <= length1; i++)
	{
		for (int l = 1; l <= length2; l++)
		{
			if (STR1[i] == STR2[l])dp[i][l] =dp[i][l-1]+1;
			else
			{
				dp[i][l]=max(dp[i - 1][l], dp[i][l - 1]);
			}
		}
	}
	return dp[length1][length2];
}
int main()
{
	int q;
	cin >> q;
	for (int i = 0; i < q; i++)
	{
		string str1, str2;
		cin >> str1 >> str2;
		cout << LCS(str1, str2) << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <stdio.h>
#include <string>
#include <cmath>

#define MAX_LENGTH 1000
#define NIL -1
using namespace std;
//think easy make easy

int q;//num of datasets
string X;
string Y;
char map[MAX_LENGTH+1][MAX_LENGTH+1];

int findMaxLength(int x,int y){//x:Xの終端.y:Yの終端(0オリジン)
	if(x < 0 || y < 0) return 0;
	if(map[x][y] == NIL){
		if(X.at(x) == Y.at(y)){
			return findMaxLength(x-1,y-1) +1;
		}else{
			return max(findMaxLength(x-1,y),findMaxLength(x,y-1));
		}
	}else return map[x][y];
}

int main(){
	
	scanf("%d",&q);

	for(int i=0;i<q;i++){
		cin >>X; cin >> Y;
		for(int i=0;i<X.size();i++){
			for(int j=0;j<Y.size();j++){
				map[i][j] = NIL;
			}
		}
	
		cout <<findMaxLength(X.size()-1,Y.size()-1) <<endl;
	}

	return 0;
}

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;
  C[0][0] = 0
  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]);
      }
      maxl = max(maxl, c[i][j]);
    }
  }javascript:void(0)

  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;
}