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

using namespace std;
static const int N = 1000;

int lenCommon(string s1, string s2)
{
	int len = max(int(s1.size()), int(s2.size()));
	vector<vector<int>> dp(N+1, vector<int>(N+1, 0));

	s1 = " " + s1;
	s2 = " " + s2;

	for (int i = 0; i <= len; ++i) dp[i][0] = 0;
	for (int i = 0; i <= len; ++i) dp[0][i] = 0;

	int ret = 0;
	for (int i = 1; i <= len; ++i)
	{
		for (int j = 1; j <= len; ++j)
		{
			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]);
		}
	}
	return ret;
}

int main()
{
	string s1, s2;
	int num; cin >> num;
	for (int i = 0; i < num; ++i)
	{
		cin >> s1 >> s2;
 		int res = lenCommon(s1, s2);
		cout << res << endl;
	}
}

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

int Longest(string x, string y) {
  int L[1001][1001];
  int maxl = -1;
  int xlen = x.size();
  int ylen = y.size();

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

  for (int i = 1; i <= xlen; i++) L[i][0] = 0;
  for (int j = 1; j <= ylen; j++) L[0][j] = 0;

  for (int i = 1; i <= xlen; i++) {
    for (int j = 1; j <= ylen; j++) {
      if (x[i] == y[j])
        L[i][j] = L[i-1][j-1] + 1;
      else
        L[i][j] = max(L[i][j-1], L[i-1][j]);
      
      maxl = max(maxl, L[i][j]);
    }
  }
  
  return maxl;
}

int main() {
  string X, Y;
  int n;
  int result[10000];

  cin >> n;
  
  for (int i = 0; i < n; i++) {
    cin >> X;
    cin >> Y;
    result[i] =  Longest(X, Y);
  }
  
  for (int i = 0; i < n; i++)
    cout << result[i] << endl;

  return 0;
}

C++: #include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<vector>
#include<queue>
#include<map>
#include<tuple>
#define rep(index,num) for(int index=0;index<num;index++)
#define rep1(index,num) for(int index=1;index<=num;index++)
#define scan(argument) cin>>argument
#define prin(argument) cout<<argument<<endl
#define kaigyo cout<<endl
#define eps 1e-15
#define mp(a1,a2) make_pair(a1,a2)
typedef long long ll;
using namespace std;
typedef pair<ll,ll> pll;
typedef pair<int,int> pint;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef vector<pint> vpint;
typedef vector<pll> vpll;
ll INFl=1e+18+1;
int INF=1e+9+1;
int main(){
	int N;
	scan(N);
	rep(i,N){
		string X,Y;
		scan(X);scan(Y);
		int dp[1001][1001]={{}};
		rep1(x,X.size()){
			rep1(y,Y.size()){
				int v=dp[x-1][y-1]+(X[x-1]==Y[y-1]);
				if(dp[x-1][y]>v) v=dp[x-1][y];
				if(dp[x][y-1]>v) v=dp[x][y-1];
				dp[x][y]=v;
			}
		}
		prin(dp[X.size()][Y.size()]);
	}
	return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
    using namespace std;
int lcs(string x,string y){
    int c[1010][1010];
    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=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]);
        }
        
    }
    return maxl;
}
int main(){
    int q;
    string x;
    string y;
    scanf("%d",&q);
    for (int i=0; i<q; i++) {
        cin>>x>>y;
        cout<<lcs(x, y)<<endl;
    }
    return 0;
}

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

using namespace std;

int dp[1001][1001];

int lcs(string x, string y) {
    int lx = x.size(), ly = y.size();
    for (int i = 1; i <= ly; ++i) {
        for (int j = 1; j <= lx; ++j) {
            dp[i][j] = max(max(dp[i - 1][j], dp[i][j - 1]), dp[i - 1][j - 1] + (x[j - 1] == y[i - 1]));
        }
    }
    return dp[ly][lx];
}

int main() {
    int n;
    string x, y;
    cin >> n;
    while (n--) {
        cin >> x >> y;
        cout << lcs(x, y) << endl;
    }

    return 0;
}

C++: 	#include <bits/stdc++.h>
	using namespace std;
	#define IOS ios::sync_with_stdio(false), cin.tie(0)
	#define REP(i, n) for (int i = 0; i < n; i++)
	#define FOR(i, a, b) for (int i = a; i < b; i++)
	#define ALL(x) (x).begin(), (x).end()
	#define dump(x) cout << (x) << endl
	#define LMAX 9223372036854775807LL
	#define LMIN -9223372036854775807LL

	using ll = long long;
	template<typename T>
	using vec = vector<T>;
	using P = pair<ll, ll>;

	template <typename A, size_t N, typename T>
	void Fill(A (&array)[N], const T &val){
		fill((T *)array, (T *)(array + N), val);
	}
	
	const ll INF = 1e18;
	const ll MOD = 1e9 + 7;

	//int dx[4] = {1,0,-1,0};
	//int dy[4] = {0,1,0,-1};
	//ll pas[51][52];
	
	signed main(){
		IOS;
		ll q;
		cin >> q;
		REP(i, q){
			string s, t;
			cin >> s >> t;
			int n = s.size();
			int m = t.size();
			vec<vec<ll>> dp(n + 1,vec<ll>(m + 1,0));
			REP(i, n)REP(j, m){
				if(s[i] == t[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]);
			}
			dump(dp[n][m]);
		}
	}

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

static const int max_n = 1000;
string s1, s2;
int q, c[max_n + 1][max_n + 1];

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

int main(void){
	cin >> q;
	for( int i = 1; i <= q; i++ ){
		cin >> s1 >> s2;
		cout << lcs(s1, s2) << endl;
	}
	return 0;
}