Leetcode_Python 303 区域和检索 - 数组不可变

解题思路

以 nums = [-2, 0, 3, -5, 2, -1]为例

• 第一步先制定一个列表，元素是前n项元素的和list = [0, -2, -2, 1, -4, -2, -3]，首项除外
• 第二步求(i,j)的总和，即list[j+1]-list[i]

代码

class NumArray(object):

    def __init__(self, nums):
        """
        :type nums: List[int]
        """
        self.nums = nums
        self.list = [0]
        for i in range(0,len(self.nums)):
            self.list.append(self.nums[i]+self.list[i])
            
    def sumRange(self, i, j):
        """
        :type i: int
        :type j: int
        :rtype: int
        """
        return (self.list[j+1]-self.list[i])

# Your NumArray object will be instantiated and called as such:
# obj = NumArray(nums)
# param_1 = obj.sumRange(i,j)