303. Range Sum Query - Immutable

https://leetcode.com/problems/range-sum-query-immutable/

JavaScript

/**
 * @constructor
 * @param {number[]} nums
 */
var NumArray = function(nums) {
  var sums = [];
  for (var i = 0; i < nums.length; i++) {
    sums[i] = i === 0 ? nums[0] : (sums[i - 1] + nums[i]);
  }
  this.sums = sums;
};

/**
 * @param {number} i
 * @param {number} j
 * @return {number}
 */
NumArray.prototype.sumRange = function(i, j) {
  var sums = this.sums;
  return i === 0 ? sums[j] : (sums[j] - sums[i - 1]);
};


/**
 * Your NumArray object will be instantiated and called as such:
 * var numArray = new NumArray(nums);
 * numArray.sumRange(0, 1);
 * numArray.sumRange(0, 2);
 */

Python

class NumArray(object):

    def __init__(self, nums):
        """
        initialize your data structure here.
        :type nums: List[int]
        """
        self.sums = []
        for i in range(len(nums)):
            self.sums.append(nums[i] if i == 0 else self.sums[i - 1] + nums[i])

    def sumRange(self, i, j):
        """
        sum of elements nums[i..j], inclusive.
        :type i: int
        :type j: int
        :rtype: int
        """
        return self.sums[j] if i == 0 else self.sums[j] - self.sums[i - 1]


# Your NumArray object will be instantiated and called as such:
# numArray = NumArray(nums)
# numArray.sumRange(0, 1)
# numArray.sumRange(1, 2)