628. Maximum Product of Three Numbers

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.

Solution:

1） scan the array, find the largest, the second largest and the third largest number.

2)   scan the array, find the smallest, the second smallest number.

3)   find maximum product of maxA * maxB * maxC and maxA * minB * minC

    public int maximumProduct(int[] nums) {
        int maxA = Integer.MIN_VALUE, maxB = Integer.MIN_VALUE, maxC = Integer.MIN_VALUE;
        int minA = Integer.MAX_VALUE, minB = Integer.MAX_VALUE;
        for(int i = 0; i < nums.length; i++){
            if(nums[i] > maxA){
                maxC = maxB;
                maxB = maxA;
                maxA = nums[i];
            }else if(nums[i] > maxB){
                maxC = maxB;
                maxB = nums[i];
            }else if(nums[i] > maxC){
                maxC = nums[i];
            }
            if(nums[i] < minA){
                minB = minA;
                minA = nums[i];
            }else if(nums[i] < minB){
                minB = nums[i];
            }
        }
        return Math.max(maxA * maxB * maxC, maxA * minA * minB);
    }