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 { public: int nthUglyNumber(int n) { int* arr=(int*)malloc(sizeof(int)*n); int index_2=0,index_3=0,index_5=0; int val_2=2, val_3=3, val_5=5; arr[0]=1; for(int i=1;i<n;i++){ arr[i]=min(min(val_2,val_3),val_5); if(arr[i]==val_2) val_2=arr[++index_2]*2; if(arr[i]==val_3) val_3=arr[++index_3]*3; if(arr[i]==val_5) val_5=arr[++index_5]*5; } return arr[n-1]; } };