Problem
Given an integer array nums
, handle multiple queries of the following type:
- Calculate the sum of the elements of
nums
between indicesleft
andright
inclusive whereleft <= right
.
Implement the NumArray
class:
NumArray(int[] nums)
Initializes the object with the integer arraynums
.int sumRange(int left, int right)
Returns the sum of the elements ofnums
between indicesleft
andright
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 tosumRange
.
Solution
/**
* @param {number[]} nums
*/
var NumArray = function(nums) {
this.leftSum = Array(nums.length);
for (var i = 0; i < nums.length; i++) {
this.leftSum[i] = (this.leftSum[i - 1] || 0) + nums[i];
}
};
/**
* @param {number} left
* @param {number} right
* @return {number}
*/
NumArray.prototype.sumRange = function(left, right) {
return this.leftSum[right] - (this.leftSum[left - 1] || 0);
};
/**
* Your NumArray object will be instantiated and called as such:
* var obj = new NumArray(nums)
* var param_1 = obj.sumRange(left,right)
*/
Explain:
nope.
Complexity:
- Time complexity : O(1).
- Space complexity : O(n).