[leetcode] 313. Super Ugly Number

Write a program to find the nth super ugly number.

Super ugly numbers are positive numbers whose all prime factors are in the given prime list primes of size k. For example, [1, 2, 4, 7, 8, 13, 14, 16, 19, 26, 28, 32] is the sequence of the first 12 super ugly numbers given primes = [2, 7, 13, 19] of size 4.

Note:
(1) 1 is a super ugly number for any given primes.
(2) The given numbers in primes are in ascending order.
(3) 0 < k ≤ 100, 0 < n ≤ 106, 0 < primes[i] < 1000.

解法一：

完全思路，看的大神的解法。维护一个数组idx，保存当前的元素下一次应该与res里的哪一个元素相乘。如果是最小的元素，则更新idx。

class Solution {public:    int nthSuperUglyNumber(int n, vector<int>& primes) {        vector<int> res(1,1), idx(primes.size(),0);        while(res.size()<n){            vector<int> tmp;            int mn = INT_MAX;            for(int i=0; i<primes.size();i++)                tmp.push_back(res[idx[i]]*primes[i]);                        for(int i=0; i<primes.size();i++)                mn = min(mn,tmp[i]);                        for(int i=0; i<primes.size();i++){                if(tmp[i]==mn) ++idx[i];            }            res.push_back(mn);        }        return res.back();    }};