https://leetcode.com/problems/ugly-number-ii/
Write a program to find the $n_{th}$ ugly number.
Ugly numbers are positive numbers whose prime factors only include $2, 3, 5.$ For example,$ 1, 2, 3, 4, 5, 6, 8, 9, 10, 12$,is the sequence of the first $10$ ugly numbers.
Note that 1 is typically treated as an ugly number.
class Solution {
private:
typedef unsigned long long int ull;
struct cmp {
bool operator()(const ull a, const ull b) {
return a > b;
}
};
public:
int nthUglyNumber(int n) {
ull lb = 0, ub = 0, arr[3] = { 2, 3, 5 };
priority_queue<ull, vector<ull>, cmp > q;
q.push(1);
for (int i = 1; i <= n;) {
ull val = q.top(); q.pop();
ub = val;
if (ub == lb) {
continue;
} else {
lb = val;
i++;
}
for (int j = 0; j < 3; j++) q.push(val * arr[j]);
}
return (int)lb;
}
};
原文：http://www.cnblogs.com/GadyPu/p/5020591.html