Sign of the Product of an Array

Sign of the Product of an Array

Leetcode Daily Challenge (2nd May, 2023)

Problem Statement:-

There is a function signFunc(x) that returns:

  • 1 if x is positive.

  • -1 if x is negative.

  • 0 if x is equal to 0.

You are given an integer array nums. Let product be the product of all values in the array nums.

Return signFunc(product).

Link: https://leetcode.com/problems/sign-of-the-product-of-an-array/description/

Problem Explanation with examples:-

Example 1

Input: nums = [-1,-2,-3,-4,3,2,1]
Output: 1
Explanation: The product of all values in the array is 144, and signFunc(144) = 1

Example 2

Input: nums = [1,5,0,2,-3]
Output: 0
Explanation: The product of all values in the array is 0, and signFunc(0) = 0

Example 3

Input: nums = [-1,1,-1,1,-1]
Output: -1
Explanation: The product of all values in the array is -1, and signFunc(-1) = -1

Constraints

  • 1 <= nums.length <= 1000

  • -100 <= nums[i] <= 100

Intuition:-

  • If we have the count of negative numbers in the array, we can easily determine the sign of the product.

  • If the count is even, the product is positive. If the count is odd, the product is negative.

  • If the array contains a zero, the product is zero.

Solution:-

  • Initialize a variable nc to 0. This variable will store the count of negative numbers in the array.

  • Iterate over the array. If the current element is negative, increment nc by 1.

  • If the current element is zero, return 0.

  • After the loop completes, return 1 if nc is even, else return -1.

Code:-

JAVA Solution

class Solution {
    public int arraySign(int[] nums) {
        int nc = 0;
        for (int i : nums) {
            if (i < 0)
                nc += 1;
            if (i == 0)
                return 0;
        }
        return (nc % 2 == 0) ? 1 : -1;
    }
}

Python Solution

class Solution:
    def arraySign(self, nums: List[int]) -> int:
        nc = 0
        for i in nums:
            if i < 0:
                nc += 1
            if i == 0:
                return 0
        return 1 if nc%2==0 else -1

Complexity Analysis:-

TIME:-

The time complexity is O(n) where n is the length of the array. We iterate over the array once.

SPACE:-

The space complexity is O(1) since we do not use any extra space.

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