Q:
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.
給定一個整型數組,求給定下標
solution:
這道題最簡單的方法就是每次輸入
我們可以預先把數組前
那麼
注意當
class NumArray {
public:
NumArray(vector<int> &nums) {
int sum=0;
for(int i = 0; i < nums.size(); i++){
sum+=nums[i];
sums.push_back(sum);
}
}
int sumRange(int i, int j) {
if(i==0)return sums[j];
return sums[j]-sums[i-1];
}
vector<int>sums;
};