is a hero! Personally, I love his first C++ solution.

1 class Solution { 2 public: 3     int nthUglyNumber(int n) { 4         vector
     
       ugly(n, 1); 5         int c2 = 2, c3 = 3, c5 = 5; 6         int i2 = 0, i3 = 0, i5 = 0; 7         for (int i = 1; i < n; i++) { 8             int last = ugly[i] = min(c2, min(c3, c5)); 9             while (c2 <= last) c2 = 2 * ugly[++i2];10             while (c3 <= last) c3 = 3 * ugly[++i3];11             while (c5 <= last) c5 = 5 * ugly[++i5];12         }13         return ugly[n - 1];14     }15 };
     

Well, refer to for more about ugly numbers!