1.描述
Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.
Example:
Given nums = [-2, 0, 3, -5, 2, -1]
sumRange(0, 2) -> 1
sumRange(2, 5) -> -1
sumRange(0, 5) -> -3
Note:
You may assume that the array does not change.
There are many calls to sumRange function.
2.分析
3.代碼
class NumArray {
public:
NumArray(vector<int> nums) {
sum.push_back(0);
for (int n : nums) {
sum.push_back(sum.back() + n);
}
}
int sumRange(int i, int j) {
return sum[j + 1] - sum[i];
}
private:
vector<int> sum;
};
/**
* Your NumArray object will be instantiated and called as such:
* NumArray obj = new NumArray(nums);
* int param_1 = obj.sumRange(i,j);
*/
