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.
solution:
本题很简单，就考察了类的使用
code:
class NumArray {
public:
NumArray(vector<int> nums) {
accu.push_back(0);
for (int num : nums)
accu.push_back(accu.back() + num);
}
int sumRange(int i, int j) {
return accu[j + 1] - accu[i];
}
private:
vector<int> accu;
};