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] = dp[i-1][j-1]+1
				} else if S[i-1] != T[j-1] && dp[i-1][j] > dp[i][j-1] {
					dp[i][j] = dp[i-1][j]
				} else {
					dp[i][j] = dp[i][j-1]
				}
				// 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++: //#if 0
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//?????????????????§???????????§???AOJ?????????????????????Runtime Error??????????????????????????????
//??£????????¨??????????????????????????????????????????????????????Runtime Error???????????¨???????????????
//??§???????????????????????????????????§???
//#endif
#include<iostream>
#include<string>
#define lth 1010

using namespace std;

int main()
{
	int n, L[1010][1010], Lmax = 0, *save;
	string *Xi, *Yi;
	cin >> n;
	save = new int[n];
	if (n <= 20)
	{
		Xi = new string[lth];
		Yi = new string[lth];
	}
	else
	{
		Xi = new string[1010];
		Yi = new string[1010];
	}
	for (int k = 0; k < n; k++)
	{
		Lmax = 0;
		string X, Y;
		cin >> X >> Y;
		for (int i = 0; i <= X.length(); i++)
		{
			if (i != 0)
				Xi[i] = X.substr(0, i );
		}
		for (int i = 0; i <= Y.length(); i++)
		{
			if (i != 0)
				Yi[i] = Y.substr(0, i );
		}
		for (int i = 0; i <= X.length(); i++)
			for (int j = 0; j <= Y.length(); j++)
			{
				if (i == 0 || j == 0)
					L[i][j] = 0;
				else if (Xi[i][i - 1] == Yi[j][j - 1])
				{
					L[i][j] = L[i - 1][j - 1] + 1;
				}
				else
				{
					L[i][j] = (L[i][j - 1] > L[i - 1][j]?L[i][j - 1] : L[i - 1][j]);
				}
				if (Lmax < L[i][j]) Lmax = L[i][j];
			}
		save[k] = Lmax;
	}

	for (int i = 0; i < n; i++)
		cout << save[i] << endl;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MOD = 1e9 + 7;
const ll INF = 1LL << 60;
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define debug(x) cerr << #x << ": " << x << endl;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

int main() {
    ll q;
    cin >> q;
    rep(i, q) {
        string s, t;
        cin >> s >> t;
        ll n = s.size(), m = t.size();
        ll dp[1100][1100] = {0};
        rep(i, n) rep(j, m) {
            if(s[i] == t[j]) dp[i+1][j+1] = max({dp[i][j] + 1, dp[i+1][j], dp[i][j+1]});
            else dp[i+1][j+1] = max(dp[i][j+1], dp[i+1][j]);
        }
        cout << dp[n][m] << endl;
    }
}

C++: #include <bits/stdc++.h>
using namespace std;
struct cww{cww(){ios::sync_with_stdio(false);cin.tie(0);}}star;
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define vv(type, c, m, n, i) vector<vector<type>> c(m, vector<type>(n, i));
#define rep(i,a,n) for(int i=(a), i##_len=(n); i<i##_len; ++i)
#define rrep(i,a,n) for(int i=(a), i##_len=(n); i>i##_len; --i)
#define len(x) ((int)(x).size())
#define mp make_pair
#define eb emplace_back
typedef long long ll;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long long> vll;
typedef vector<string> vs;
typedef vector<bool> vb;
constexpr int MAX = 1005;
inline int lcs(string X, string Y) {
	vv(int, c, MAX, MAX, 0);
	int m = len(X);
	int n = len(Y);
	int maxl = 0;
	X = ' ' + X;
	Y = ' ' + Y;
	rep(i, 1, m + 1) {
		rep(j, 1, n + 1) {
			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]);
			if(maxl < c[i][j]) maxl = c[i][j];
		}
	}
	return maxl;
}
int main() {
	int n; cin >> n;
	string s1, s2;
	rep(i, 0, n) {
		cin >> s1 >> s2;
		P(lcs(s1, s2));
	}
	return 0;
}

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

using namespace std;
static const int N=1000;
int lcs(string X, string Y){
    int m=X.size();
    int n=Y.size();
    int c[N+1][N+1];
    int maxl=0;
    X=' '+X;
    Y=' '+Y;
    int i,j;
    for(i=1;i<=m;i++)c[i][0]=0;
    for(j=1;j<=n;j++)c[0][j]=0;

    for(i=1;i<=m;i++){
        for(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][j-1],c[i-1][j]);
            }
            maxl=max(maxl,c[i][j]);
        }
    }
    return maxl;
}
int main()
{
    int n;
    string s1,s2;
    cin>>n;
    for(int i=0;i<n;i++){
        cin>>s1>>s2;
        cout<<lcs(s1,s2)<<endl;
    }

    return 0;
}

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

int lcs(string s, string t);
int main(){
  int n; cin >> n;
  string s, t;
  for(int i=0; i<n; i++){
    cin >> s >> t;
    cout << lcs(s, t) << endl;
  }

  return 0;
}

int lcs(string s, string t){
  int ans=0;
  int sl=s.length(), tl=t.length();
  int dp[s.length()+1][t.length()+1];
  dp[0][0]=0;
  for(int i=1; i<=sl; i++) dp[i][0]=0;
  for(int j=1; j<=tl; j++) dp[0][j]=0;

  for(int i=1; i<=sl; i++){
    for(int j=1; j<=tl; j++){
      if(i==0 || j==0) dp[i][j]=0;
      else if(s[i]==t[j]) dp[i][j]=dp[i-1][j-1]+1;
      else dp[i][j]=max(dp[i][j-1], dp[i-1][j]);

      ans = max(ans, dp[i][j]);
    }

  }
  return ans;
}

C++: 

#include<iostream>
#include<string>
#include<algorithm>
#define N 1000
using namespace std;
int lcs(string X, string Y) {
  int c[N + 1][N + 1];
  int m = X.size();
  int n = Y.size();
  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 - 1] == Y[j - 1] ){
        c[i][j] = c[i - 1][j - 1] + 1;
      } else {
        c[i][j] = max(c[i][j - 1], c[i - 1][j]);
      }
    }
  }
  return c[m][n]
}
int main(){
  int n;
  cin >> n;
  for ( int i = 0; i < n; ++i ){
  string s1, s2;
    cin >> s1 >> s2;
    cout << lcs(s1, s2) << endl;
  }
  return 0;
}