628. Maximum Product of Three Numbers

contest38的签到题。我用了sort:

public class MaximumProduct {
    public int maximumProduct(int[] nums) {
        if (nums.length < 3) return 0;
        if (nums.length == 3) return nums[0] * nums[1] * nums[2];
        int len = nums.length;
        Arrays.sort(nums);
//      if (nums[1] >= 0) {
//          return nums[len - 1] * nums[len - 2] * nums[len - 3];
//      }
        return Math.max(nums[0] * nums[1] * nums[len - 1], nums[len - 1] * nums[len - 2] * nums[len - 3]);
    }
}

也可以用扫描：

public class Solution {
    public int maximumProduct(int[] nums) {
        int min1 = Integer.MAX_VALUE, min2 = Integer.MAX_VALUE;
        int max1 = Integer.MIN_VALUE, max2 = Integer.MIN_VALUE, max3 = Integer.MIN_VALUE;
        for (int n: nums) {
            if (n <= min1) {
                min2 = min1;
                min1 = n;
            } else if (n <= min2) {     // n lies between min1 and min2
                min2 = n;
            }
            if (n >= max1) {            // n is greater than max1, max2 and max3
                max3 = max2;
                max2 = max1;
                max1 = n;
            } else if (n >= max2) {     // n lies betweeen max1 and max2
                max3 = max2;
                max2 = n;
            } else if (n >= max3) {     // n lies betwen max2 and max3
                max3 = n;
            }
        }
        return Math.max(min1 * min2 * max1, max1 * max2 * max3);
    }
}