剑指offer系列26：丑数

z剑指offer这一章都是这种题型，求优化解的，尽可能降低算法的复杂度。这个题不难，首先要想清楚什么是丑数，其次，想清楚如何生成丑数。还有，如何表达生成的丑数。这个题在表达丑数的构成上的代码很巧妙。

#include<iostream>
#include<string>
#include <vector>
#include <algorithm>
//#include <sstream>
using namespace std;
class Solution {
public:
    int ugly[1000];
    int minOlivia(int a, int b, int c)
    {
        int temp = (a < b) ? a : b;
        return (temp < c) ? temp : c;
    }
    int GetUglyNumber_Solution(int index) {
        if (index == 0)
            return 0;
        ugly[0] = 1;
        int index2 = 0;
        int index3 = 0;
        int index5 = 0;
        int n = 1;
        int val=1;
        while (n < index)
        {
            val = minOlivia(ugly[index2] * 2, ugly[index3] * 3, ugly[index5] * 5);
            if (val == ugly[index2] * 2)
                index2++;
            if (val == ugly[index3] * 3)
                index3++;
            if (val == ugly[index5] * 5)
                index5++;
            ugly[n] = val;
            n++;
        }
        int re = ugly[n - 1];
        return re;

    }
};
int main()
{
    Solution so;
    //vector<int> test{ 3,5,1,4,2 };
    cout << so.GetUglyNumber_Solution(10) << endl;
    return 0;
}