丑数 代码(C)

本文地址: http://blog.csdn.net/caroline_wendy

题目: 我们把只包含因子2, 3 和 5的数称作丑数. 求按从小到大的顺序的第5个丑数.

可以设置一个数组包含所需要的丑数, 依次比较乘以2, 乘以3, 乘以5的最小的数, 最后返回结果.

如第5个丑数是5, 如1, 2, 3, 4(2*2), 5均是丑数.

代码:

/*
 * main.cpp
 *
 *  Created on: 2014.6.12
 *      Author: Spike
 */

/*eclipse cdt, gcc 4.8.1*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int Min(int number1, int number2, int number3) {
	int min = (number1 < number2) ? number1 : number2;
	min = (min < number3) ? min : number3;

	return min;
}

int GetUglyNumber(int index) {
	if (index <= 0)
		return 0;
	int* pUglyNumbers = new int[index];
	pUglyNumbers[0] = 1;
	int nextUglyIndex = 1;

	int* pMultiply2 = pUglyNumbers;
	int* pMultiply3 = pUglyNumbers;
	int* pMultiply5 = pUglyNumbers;

	while (nextUglyIndex < index) {
		int min = Min(*pMultiply2*2, *pMultiply3*3, *pMultiply5*5);
		pUglyNumbers[nextUglyIndex] = min;
		while (*pMultiply2*2 <= pUglyNumbers[nextUglyIndex])
			++pMultiply2;
		while (*pMultiply3*3 <= pUglyNumbers[nextUglyIndex])
			++pMultiply3;
		while (*pMultiply5*5 <= pUglyNumbers[nextUglyIndex])
			++pMultiply5;

		++nextUglyIndex;
	}
	int ugly = pUglyNumbers[nextUglyIndex-1];
	delete[] pUglyNumbers;
	return ugly;

}
int main(void)
{
    int num = 5;
    int result = GetUglyNumber(num);
    printf("result = %d\n", result);

    return 0;
}

result = 5