LeetCode题解(0724)：寻找数组的中心索引(Python)

题目：原题链接（简单）

解法时间复杂度空间复杂度执行用时Ans 1 (Python)$O(N^2)$$O(1)$9104ms (11.77%)Ans 2 (Python)$O(N)$$O(1)$56ms (95.05%)Ans 3 (Python)$O(N)$$O(1)$64ms (86.25%)

LeetCode的Python执行用时随缘，只要时间复杂度没有明显差异，执行用时一般都在同一个量级，仅作参考意义。

解法一（暴力解法）：

def pivotIndex(self, nums: List[int]) -> int: for i in range(len(nums)): if sum(nums[:i]) == sum(nums[i + 1:]): return i else: return -1

解法二（插值法）：

def pivotIndex(self, nums: List[int]) -> int: differ = sum(nums) for i in range(len(nums)): if i > 0: differ -= nums[i] + nums[i - 1] else: differ -= nums[i] if differ == 0: return i else: return -1

解法三：

def pivotIndex(self, nums: List[int]) -> int: total = sum(nums) left = 0 for i in range(len(nums)): if left == (total - left - nums[i]): return i left += nums[i] else: return -1