剑指 Offer 49. 丑数https://leetcode.cn/problems/chou-shu-lcof/

对每个丑数 分别乘2、乘3、乘5 即可得到后续丑数

其中只需要对计算出来的丑数结果进行去重即可

int nthUglyNumber(int n) {// base caseif (n < 1){return -1;}if (n == 1){return 1;}vector<int> res(n);res[0] = 1;int val2 = 2, val3 = 3, val5 = 5;int p2 = 0, p3 = 0, p5 = 0;int p = 1;while (p != n){int minVal = min(val2, min(val3, val5));// 去重if (minVal != res[p - 1]){res[p] = minVal;++p;}if (minVal == val2){++p2;val2 = res[p2] * 2;}else if (minVal == val3){++p3;val3 = res[p3] * 3;}else{++p5;val5 = res[p5] * 5;}}return res[n - 1];
}