Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

type Position struct {
	X int
	Y int
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)
	n, err := nextInt(sc)
	if err != nil {
		panic(err)
	}
	for i := 0; i < n; i++ {
		strX := nextText(sc)
		strY := nextText(sc)
		fmt.Println(calcLcs(strX, strY))
	}
}

func calcLcs(strX, strY string) int {
	return lcs(strX, strY, Position{0, 0}, make(map[Position]int))
}

func lcs(strX string, strY string, position Position, memo map[Position]int) int {
	if position.X >= len(strX) || position.Y >= len(strY) {
		return 0
	}
	if v, ok := memo[position]; ok {
		return v
	}
	if strX[position.X] == strY[position.Y] {
		result := lcs(strX, strY, Position{position.X + 1, position.Y + 1}, memo)
		memo[position] = result + 1
		return memo[position]
	} else {
		result1 := lcs(strX, strY, Position{position.X + 1, position.Y}, memo)
		result2 := lcs(strX, strY, Position{position.X, position.Y + 1}, memo)
		var result int
		if result1 > result2 {
			result = result1
		} else {
			result = result2
		}
		memo[position] = result
		return result
	}
}

func nextInt(sc *bufio.Scanner) (int, error) {
	sc.Scan()
	return strconv.Atoi(sc.Text())
}

func nextText(sc *bufio.Scanner) string {
	sc.Scan()
	return sc.Text()
}

C++: #include <bits/stdc++.h>
#define rep(i,n) for(int i=0; i<(n); i++)
#define FOR(i,a,n) for(int i=(a); i<(n); i++)
#define all(v) v.begin(), v.end()
#define fi first
#define se second
using namespace std;
using ll = long long;
using P = pair<int ,int>;
const int INF = 1e9;
const int MOD = 1e9+7;

void print() { cout << endl; }
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) { cout << head << ((sizeof...(tail)!=0)?" ":""); print(forward<Tail>(tail)...); }
template <class T> void print(vector<T> &vec) { for (auto& a : vec) { cout << a << ((&a!=&vec.back())?" ":""); } cout << endl; }
template <class T> void print(vector<vector<T>> &df) { for (auto& vec : df) { print(vec); } }

int dp[1010][1010];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n; cin >> n;
    rep(_, n) {
        string s, t; cin >> s >> t;
        memset(dp, 0, sizeof(dp));
        int n = s.length(), m = t.length();
        rep(i, n) rep(j, m) {
            char a = s[i], b = t[j];
            if (a==b) 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[n][m] << endl;
    }
}

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.xize();
	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() {
	
	string s1, s2;
	int n; cin >> n;
	for(int i = 0; i < n; i++){
		cin >> s1 >> s2;
	    cout << lcs(s1, s2) << end1;
	}
	
	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;
  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(){
  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 <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;
}