题解 | #丑数#

#include <queue>
class Solution {
 public:
  /**
   * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
   *
   *
   * @param index int整型
   * @return int整型
   */
  int GetUglyNumber_Solution(int index) {
    // write code here
    //排除0
    if (index == 0 ) {
      return 0;
    }
    priority_queue<long, vector<long>, greater<long>> pq;
    unordered_set<long> uset;
    pq.push(1);
    int i = 0;
    uset.insert(1);
    vector<int> prim = {2, 3, 5};
    long top_value = 0;
    while ( i < index ) {
      top_value = pq.top();
    
      pq.pop();
      i++;
      for (auto num : prim) {
        int tem = num * top_value;
        if (uset.count(tem) != 0) {
          continue;
        } else {
          uset.insert(tem);
          pq.push(num * top_value);
        }

      }
    }
    return top_value;
  }
};

如果x是丑数，则2x, 3x, 5x均是丑数。