Python_Lintcode_1068

最新推荐文章于 2023-09-03 12:25:34 发布

hehehe_py

最新推荐文章于 2023-09-03 12:25:34 发布

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本文链接：https://blog.youkuaiyun.com/hehehe_py/article/details/80753179

本文介绍了一种高效的方法来找到一个整数数组中的“中心”索引，该索引左边所有元素的总和等于其右边所有元素的总和。通过避免重复计算整个数组的总和，此方法显著提高了搜索效率。

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Given an array of integers nums, write a method that returns the "pivot" index of this array.

We define the pivot index as the index where the sum of the numbers to the left of the index is equal to the sum of the numbers to the right of the index.

If no such index exists, we should return -1. If there are multiple pivot indexes, you should return the left-most pivot index.

求一个数组中左边之和等于右边之和的数的索引值

本来想直接循环加sum(nums[:i])

但是时间复杂度太大，测试只能过40%，然后改啊改

class Solution:
    """
    @param nums: an array
    @return: the "pivot" index of this array
    """
1    def pivotIndex(self, nums):
        # Write your code here
        if nums == []:
            return -1
        else:
            i = 0
            sum_1 = 0
            sum_2 = sum(nums)
            while i < len(nums):
                sum_3 =sum_2 - sum_1 - nums[i]
                if sum_1 == sum_3:
                    return i
                    break
                sum_1 += nums[i]
                i+=1
                if i == len(nums):
                    return -1