Ugly Number II 寻找第N个丑数

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​​sequence of the first ​​10​​Note that ​​1​​

class Solution {
public:
    int nthUglyNumber(int n) {
        
        /*
        超时
        if(n==1)
            return 1;
        int k=1;
        int tmp;
        int ans=1;
        while(k<n)
        {
            tmp=++ans;
            while(1)
            {
                while(tmp%2==0)
                    tmp/=2;
                while(tmp%3==0)
                    tmp/=3;
                while(tmp%5==0)
                    tmp/=5;
                if(tmp==1)
                    break;
                else
                    tmp=++ans;
            }
            k++;
        }
        return ans;
        */
        
        //记住14不是的，不能用3个index，然后遍历比较
        //因为每个丑数都是前面的丑数*2，*3，*5得到，所以要从以前的数中拿取
        
        int *ans=new int[n+1];
        ans[0]=1;
        int index=1;
        int i=0,j=0,k=0;
        while(index<n)
        {
            ans[index]=min(ans[i]*2,min(ans[j]*3,ans[k]*5));
            if(ans[index]==ans[i]*2)
                i++;
            if(ans[index]==ans[j]*3)
                j++;
            if(ans[index]==ans[k]*5)
                k++;
            index++;
        }
        return ans[index-1];
        
    }
};