20221027 - 1822. Sign of the Product of an Array 数组元素积的符号（遍历）

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).

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

Solution

遍历

class Solution {
public:
    int arraySign(vector<int>& nums) {
        int ret = 1;
        for (int i = 0; i < nums.size(); i++) {
            if (ret * nums[i] < 0) ret = -1;
            else if (ret * nums[i] > 0) ret = 1;
            else return 0;
        }
        return ret;
    }
};

优化

只需要更新符号位即可，注意乘法运算的时间比比较运算长

class Solution {
public:
    int arraySign(vector<int>& nums) {
        int ret = 1;
        for (int i = 0; i < nums.size(); i++) {
            if (nums[i] == 0) return 0;
            else if (nums[i] < 0) ret = -ret;
        }
        return ret;
    }
};

题目链接：1822. 数组元素积的符号 - 力扣（LeetCode）