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303.range-sum-query-immutable.py
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56 lines (49 loc) · 1.61 KB
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# Tag: Array, Design, Prefix Sum
# Time: O(*1)
# Space: O(N)
# Ref: -
# Note: -
# Given an integer array nums, handle multiple queries of the following type:
#
# Calculate the sum of the elements of nums between indices left and right inclusive where left <= right.
#
# Implement the NumArray class:
#
# NumArray(int[] nums) Initializes the object with the integer array nums.
# int sumRange(int left, int right) Returns the sum of the elements of nums between indices left and right inclusive (i.e. nums[left] + nums[left + 1] + ... + nums[right]).
#
#
# Example 1:
#
# Input
# ["NumArray", "sumRange", "sumRange", "sumRange"]
# [[[-2, 0, 3, -5, 2, -1]], [0, 2], [2, 5], [0, 5]]
# Output
# [null, 1, -1, -3]
#
# Explanation
# NumArray numArray = new NumArray([-2, 0, 3, -5, 2, -1]);
# numArray.sumRange(0, 2); // return (-2) + 0 + 3 = 1
# numArray.sumRange(2, 5); // return 3 + (-5) + 2 + (-1) = -1
# numArray.sumRange(0, 5); // return (-2) + 0 + 3 + (-5) + 2 + (-1) = -3
#
#
# Constraints:
#
# 1 <= nums.length <= 104
# -105 <= nums[i] <= 105
# 0 <= left <= right < nums.length
# At most 104 calls will be made to sumRange.
#
#
class NumArray:
def __init__(self, nums: List[int]):
n = len(nums)
self.prefix = [0 for i in range(n + 1)]
for i in range(1, n + 1):
self.prefix[i] = self.prefix[i - 1] + nums[i - 1]
def sumRange(self, left: int, right: int) -> int:
return self.prefix[right + 1] - self.prefix[left]
# Your NumArray object will be instantiated and called as such:
# obj = NumArray(nums)
# param_1 = obj.sumRange(left,right)