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.
Inspired by official solutions:
class NumArray {
private:
// vector<int> nums_;
vector<int> sums_;
public:
NumArray(vector<int>& nums) {
// nums_ = nums;
int sum = 0;
sums_.push_back(sum);
for (const auto& num:nums) {
sum += num;
sums_.push_back(sum);
}
}
int sumRange(int i, int j) {
return sums_[j+1] - sums_[i];
}
};
/**
* Your NumArray object will be instantiated and called as such:
* NumArray* obj = new NumArray(nums);
* int param_1 = obj->sumRange(i,j);
*/
Runtime: 32 ms, faster than 69.14% of C++ online submissions for Range Sum Query - Immutable.
Memory Usage: 17.2 MB, less than 76.54% of C++ online submissions for Range Sum Query - Immutable.
