# HackerCup

## 1

// HackerCup1.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。

#include <iostream>
#include <string>

int main()
{
    int testCase = 0;
    std::cin >> testCase;
    
    for (auto i = 0; i < testCase; ++i) {
        std::string input;
        std::cin >> input;
        int Bcount = 0;

        for (const auto& v : input) {
            if (v == 'B') {
                Bcount++;
            }
        }

        auto result = 'Y';
        if (input.size() <= 2 || Bcount < (input.size() / 2) || Bcount == input.size() - 1) {
            result = 'N';
        }

        std::cout << "Case #" << std::to_string(i+1) << ": " << result << std::endl;
    }
}

## 2

// HackerCup2.cpp : 此文件包含 "main" 函数。程序执行将在此处开始并结束。

#include <iostream>
#include <string>

int main()
{
    int testCase = 0;
    std::cin >> testCase;

    for (auto i = 0; i < testCase; ++i) {
        std::string input;
        std::cin >> input;
        int Bcount = 0;

        for (const auto& v : input) {
            if (v == 'B') {
                Bcount++;
            }
        }

        auto result = 'Y';
        if (input.size() <= 2 || Bcount < 2 || Bcount == input.size() - 1) {
            result = 'N';
        }

        std::cout << "Case #" << std::to_string(i + 1) << ": " << result << std::endl;
    }
}

## 3

(x|(X&(0|(1&0))))
x| X & 0|(1&0)
x| X & 0|

0 1 23 3 3 3210
(0|(1&((1|0)|(1&0))))

((0|(1&((1|0)|(1&0))))|0)

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

static const uint64_t MOD = 1000000007;

uint64_t getPower(int unsigned y)
{
    uint64_t res = 1;     // Initialize result 
    uint64_t x = 2;
    auto p = MOD;

    while (y > 0) 
    { 
        // If y is odd, multiply x with result 
        if (y & 1) 
            res = (res*x) % p; 
  
        // y must be even now 
        y = y>>1; // y = y/2 
        x = (x*x) % p;   
    } 

    return res;
}

int solution() {
    using namespace std;
    int size, K;
    cin >> size;
    cin >> K;
    string input;
    cin >> input;
    uint64_t pay = 0;

    int cnt = 0;
    for (auto i = size - 1; i >= 0; --i) {
        switch (input[i]) {
        case 'A':
            cnt = max(0, cnt - 1);
            break;
        case 'B':
            if (cnt == K) {
                uint64_t price = 1;
                pay = (pay + getPower(i+1)) % MOD;
                cnt --;
            }
            else {
                cnt++;
            }
            break;
        }
    }
    return pay;
}

int main()
{
    int testCase = 0;
    std::cin >> testCase;

    for (auto i = 0; i < testCase; ++i) {
        const auto result = solution();
        std::cout << "Case #" << i + 1 << ": " << result << std::endl;
    }

    return 0;
}

## 4

先說一下理解

題目輸入 N 個節點，提出 M 個需求，需求為針對 Node A ＆ B 的 LCA 必須為 C

輸入為

CASE
M N
A B C
A B C...
M N
A B C
A B C...

輸出為：
CASE 1 : AP BP CP

如果自己已經是 root 則顯示 0