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>
typedef long long ll;
typedef long double ld;
#define rep(i,n) for(ll i=0;i<(n);i++)
#define repr(i,n) for(ll i=(n-1);i>=0;i--)
#define all(x) x.begin(),x.end()
#define br cout << "\n";
using namespace std;
const long long INF = 1e9;
const long long MOD = 1e9+7;
using Graph = vector<vector<ll>>;
template<class T> inline bool chmin(T &a, T b) { if(a > b){ a = b; return true;} return false;}
template<class T> inline bool chmax(T &a, T b) { if(a < b){ a = b; return true;} return false;}

// 0 false, 1 true 
// string to int : -48
// a to A : -32
// ceil(a)  1.2->2.0
// c++17	g++ -std=c++17 a.cpp

int main() {
    std::cout << std::fixed << std::setprecision(15);
    ll q; cin >> q;
    rep(Q, q){
        string s, t; cin >> s >> t;
        ll s_size = s.size(), t_size = t.size();

        vector<vector<ll>> dp(s_size+1, vector<ll>(t_size+1));

        for(ll i = 0; i < s_size; i++){
            for(ll j = 0; j < t_size; j++){
                if(s[i] == t[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[s_size][t_size] << endl;

    }

}

C++: #include <iostream>
#include <cstring>
using namespace std;
char sz1[1000];
char sz2[1000];
int maxLen[1000][1000];
int main(){
int n;
cin>>n;
while( cin >> sz1 >> sz2 ){
int length1 = strlen( sz1);
int length2 = strlen( sz2);
int nTmp;
int i,j;
for( i = 0;i <= length1; i ++ )
maxLen[i][0] = 0;
for( j = 0;j <= length2; j ++ )
maxLen[0][j] = 0;
for( i = 1;i <= length1;i ++ ) {
for( j = 1; j <= length2; j ++ ){
if( sz1[i-1] == sz2[j-1] )
maxLen[i][j] = maxLen[i-1][j-1] + 1;
else
maxLen[i][j] = max(maxLen[i][j-1],maxLen[i-1][j]);
}
}
cout << maxLen[length1][length2] << endl;
n--;
if(n<1)break;
}
return 0;
}

C++: #include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <string>
#include <vector>

// Acknowledgement: Special thanks to kyomukyomupurin, who developed this
// template.
template <class T, class U>
std::ostream& operator<<(std::ostream& os, const std::pair<T, U>& p) {
  return os << '(' << p.first << ", " << p.second << ')';
}

template <class T>
std::ostream& operator<<(std::ostream& os, const std::vector<T>& vec) {
  int n = 0;
  for (auto e : vec) os << (n++ ? ", " : "{") << e;
  return os << (n ? "}" : "{}");
}

template <class T>
std::ostream& operator<<(std::ostream& os, const std::set<T>& st) {
  int n = 0;
  for (auto e : st) os << (n++ ? ", " : "{") << e;
  return os << (n ? "}" : "{}");
}

template <class T, class U>
std::ostream& operator<<(std::ostream& os, const std::map<T, U>& mp) {
  int n = 0;
  for (auto e : mp) os << (n++ ? ", " : "{") << e;
  return os << (n ? "}" : "{}");
}

template <class T>
std::istream& operator>>(std::istream& is, std::vector<T>& vec) {
  for (T& e : vec) is >> e;
  return is;
}

#ifdef LOCAL
#define debug(...) \
  std::cerr << "[" << #__VA_ARGS__ << "]: ", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

void debug_out() { std::cerr << '\n'; }

template <class Head, class... Tail>
void debug_out(Head&& head, Tail&&... tail) {
  std::cerr << head;
  if (sizeof...(Tail) != 0) std::cerr << ", ";
  debug_out(std::forward<Tail>(tail)...);
}
using namespace std;
using int64 = long long;

int main() {
  int q;
  cin >> q;
  string X, Y;
  for (int _ = 0; _ < q; _++) {
    int mx = 0;
    cin >> X >> Y;
    X = ' ' + X;
    Y = ' ' + Y;
    int X_size = X.size();
    int Y_size = Y.size();
    vector<vector<int>> dp(X_size, vector<int>(Y_size));
    for (int i = 1; i < X_size; i++) {
      for (int j = 1; j < Y_size; j++) {
        if (X[i] == Y[j]) {
          dp[i][j] = dp[i - 1][j - 1] + 1;
        } else {
          dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
        }
        mx = max(mx, dp[i][j]);
      }
    }
    cout << mx << endl;
  }
  return 0;
}

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

using namespace std;

typedef long long int ll;
typedef pair<ll, ll> pll;

#define FOR(i, n, m) for(ll (i)=(m);(i)<(n);++(i))
#define REP(i, n) FOR(i,n,0)
#define OF64 std::setprecision(10)

const ll MOD = 1000000007;
const ll INF = (ll) 1e15;

ll solve() {
    string S, T;
    cin >> S >> T;
    ll N = S.length(), M = T.length();
    vector<vector<ll>> dp(N + 1, vector<ll>(M + 1, 0));
    REP(i, N) {
        REP(j, M) {
            dp[i + 1][j + 1] = std::max(dp[i + 1][j], dp[i][j + 1]);
            if (S[i] == T[j])
                dp[i + 1][j + 1] = std::max(dp[i + 1][j + 1], dp[i][j] + 1);
        }
    }
    return dp[N][M];
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll Q;
    cin >> Q;
    REP(_, Q) {
        cout << solve() << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <string>
#include <algorithm>
const int maxn = 1010;
int num[maxn][maxn];
using namespace std;
int lcd(string x,string y){
	int m = x.size();
	int n = y.size();
	int i,j;
    x = ' '+x;
    y = ' '+y;
	for(i=0;i<=m;i++) num[i][0] = 0;
	for(j=1;j<=n;j++) num[0][j] = 0;
	for(i=1;i<=m;i++){
		for(j=1;j<=n;j++){
			if(x[i]==y[j])
				num[i][j] = num[i-1][j-1]+1;
			else
				num[i][j] = max(num[i-1][j],num[i][j-1]);	
		}	
	}
	return num[m][n];
}
int main(){
    int t;
    string a,b;
    cin>>t;
    while(t--){
    	cin>>a>>b;
    	cout<<lcd(a,b)<<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;
  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;
}