628. Maximum Product of Three Numbers--找最大乘积

Given an integer array, find three numbers whose product is maximum and output the maximum product.

Example 1:

Input: [1,2,3]
Output: 6

Example 2:

Input: [1,2,3,4]
Output: 24

Note:

1. The length of the given array will be in range [3,104] and all elements are in the range [-1000, 1000].
2. Multiplication of any three numbers in the input won't exceed the range of 32-bit signed integer.

在数组里找三个数，使乘积最大即可。想到的方法是先排序，然后按照正数有1个还是其他多个去找最大值，最大值出现的组合可能是：前2个数字和最后一个数字，最后三个数字，代码有点冗长：

Arrays.sort(nums);
		int len = nums.length;
		for(int j=0;j<len;j++){
		System.out.println(nums[j]);}
		int count=0;
		
		int i=len-1;
		int res = Integer.MIN_VALUE;
		
		while(i>=0){
			if(nums[i]>0){count++;}
			if(nums[i]<=0) {break;}
			i--;
		}
		if(count!=1){
			res = Math.max(res,nums[len-1]*nums[len-2]*nums[len-3]);
			res = Math.max(res, nums[len-1]*nums[0]*nums[1]);
		}
		if(count==1){
			res = Math.max(res,nums[len-1]*nums[0]*nums[1]);
		}
		return res;

结果，其实这样就行了==：

int len = nums.length;
		Arrays.sort(nums);
		int a = nums[0]*nums[1]*nums[len-1];
		int b = nums[len-2]*nums[len-3]*nums[len-1];
		return Math.max(a, b);