LeetCode-Solutions-in-Cpp17

Solutions to high-frequency interview questions of LeetCode in C++17, taking into account both efficiency and comprehensibility.

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• 互斥量

class Foo {
 public:
  Foo() {
    m1.lock();
    m2.lock();
  }

  void first(function<void()> printFirst) {
    // printFirst() outputs "first". Do not change or remove this line.
    printFirst();
    m1.unlock();
  }

  void second(function<void()> printSecond) {
    m1.lock();
    // printSecond() outputs "second". Do not change or remove this line.
    printSecond();
    m2.unlock();
  }

  void third(function<void()> printThird) {
    m2.lock();
    // printThird() outputs "third". Do not change or remove this line.
    printThird();
  }

 private:
  mutex m1;
  mutex m2;
};

• 信号量

#include <semaphore.h>

class Foo {
 public:
  Foo() {
    sem_init(&s1, 0, 0);
    sem_init(&s2, 0, 0);
  }

  void first(function<void()> printFirst) {
    // printFirst() outputs "first". Do not change or remove this line.
    printFirst();
    sem_post(&s1);
  }

  void second(function<void()> printSecond) {
    sem_wait(&s1);
    // printSecond() outputs "second". Do not change or remove this line.
    printSecond();
    sem_post(&s2);
  }

  void third(function<void()> printThird) {
    sem_wait(&s2);
    // printThird() outputs "third". Do not change or remove this line.
    printThird();
  }

 private:
  sem_t s1;
  sem_t s2;
};

• 条件变量

class Foo {
 public:
  Foo() {}

  void first(function<void()> printFirst) {
    unique_lock<mutex> l{m};
    // printFirst() outputs "first". Do not change or remove this line.
    printFirst();
    b1 = true;
    cv1.notify_one();
  }

  void second(function<void()> printSecond) {
    unique_lock<mutex> l{m};
    cv1.wait(l, [this] { return b1; });
    // printSecond() outputs "second". Do not change or remove this line.
    printSecond();
    b2 = true;
    cv2.notify_one();
  }

  void third(function<void()> printThird) {
    unique_lock<mutex> l{m};
    cv2.wait(l, [this] { return b2; });
    // printThird() outputs "third". Do not change or remove this line.
    printThird();
  }

 private:
  mutex m;
  condition_variable cv1;
  condition_variable cv2;
  bool b1 = false;
  bool b2 = false;
};