303-range-sum-query-immutable.md

303. Range Sum Query - Immutable - 区域和检索 - 数组不可变

给定一个整数数组  nums，求出数组从索引 i 到 j  (i ≤ j) 范围内元素的总和，包含 i,  j 两点。

示例：

给定 nums = [-2, 0, 3, -5, 2, -1]，求和函数为 sumRange()

sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3

说明:

1. 你可以假设数组不可变。
2. 会多次调用 sumRange 方法。

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题目标签：Dynamic Programming

题目链接：LeetCode / LeetCode中国

题解

Language	Runtime	Memory
python3	56 ms	N/A

class NumArray:

    def __init__(self, nums):
        """
        :type nums: List[int]
        """
        self.sums = [0]
        for i, n in enumerate(nums):
            self.sums.append(self.sums[i] + n)

    def sumRange(self, i, j):
        """
        :type i: int
        :type j: int
        :rtype: int
        """
        return self.sums[j+1] - self.sums[i]


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