303. Range Sum Query - Immutable

Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.

Implement the NumArray class:

• NumArray(int[] nums) Initializes the object with the integer array nums.
• int sumRange(int i, int j) Return the sum of the elements of the nums array in the range [i, j] inclusive (i.e., sum(nums[i], nums[i + 1], ... , nums[j]))

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 1 ((-2) + 0 + 3)
numArray.sumRange(2, 5); // return -1 (3 + (-5) + 2 + (-1))
numArray.sumRange(0, 5); // return -3 ((-2) + 0 + 3 + (-5) + 2 + (-1))

Constraints:

• 0 <= nums.length <= 104
• -105 <= nums[i] <= 105
• 0 <= i <= j < nums.length
• At most 104 calls will be made to sumRange.

# @lc code=start
using LeetCode

struct NumArray
    sums::Vector
    function NumArray(nums::Vector)
        n = length(nums)
        sums = nums[:]

        for i = 2:n
            sums[i] = sums[i-1] + nums[i]
        end
        new(sums)
    end
end

function sum_range(nums::NumArray, i::Int, j::Int)
    i == j && return 0
    i == 1 && return nums.sums[j]
    return nums.sums[j] - nums.sums[i-1]
end
# @lc code=end

sum_range (generic function with 1 method)

This page was generated using DemoCards.jl and Literate.jl.