maidamai0 / leetcode

At last...the leetcode practice.

Notes of my leetcode practicing

Structure

Every cpp file is a solution to a problem on LeetCode

Some notes about the sulution for particular problem are in the notes directory.

How to build

conan is used to manage dependency， cmake is used to generate project files, ninjia is used to build.

mkdir build
cd build
conan install ..
cmake ..
ninja

Tools I used

I use vscode with leetcode extension to do test and debug localy and submit I'm sure my solution works.

Usually I will make a brute force suluiton first and make more optimization veriosns.

Take an example:

class Solution {
public:
  vector<int> countBits(int num) { return kernighan(num); }

private:
  vector<int> brute_fource(const int num) const {
    vector<int> ret(num + 1, 0);
    constexpr auto integer_size = sizeof(int) * 8;
    for (int i = 1; i <= num; ++i) {
      unsigned char sum = 0;
      for (size_t j = 0; j < integer_size; ++j) {
        sum += (i & (int(1) << j)) > 0;
      }
      ret[i] = sum;
    }

    return ret;
  }

  vector<int> dynamic_programming(const int num) const {
    vector<int> ret(num + 1, 0);
    if (num == 0) {
      return ret;
    }

    if (num == 1) {
      ret[1] = 1;
      return ret;
    }

    ret[1] = 1;

    bool is_even = true;
    constexpr auto integer_size = sizeof(int) * 8;
    for (int i = 2; i <= num; ++i) {
      if (is_even) {
        is_even = false;
        unsigned char sum = 0;
        for (size_t j = 0; j < integer_size; ++j) {
          sum += (i & (int(1) << j)) > 0;
        }
        ret[i] = sum;
      } else {
        is_even = true;
        ret[i] = ret[i - 1] + 1;
      }
    }

    return ret;
  }

  vector<int> kernighan(const int num) {
    std::vector<int> ret(num + 1, 0);
    for (int i = 1; i <= num; ++i) {
      ret[i] = ret[i & (i - 1)] + 1;
    }
    return ret;
  }
};

Test framework

I personally like open source,modern,beautiful and lightweight tools.doctest is my choice for testing.