leetcode range sum query

 

 

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:

1. You may assume that the array does not change.
2. There are many calls to sumRange function.

 

刚开始看题，有些不懂，暴力破解后time exceed。很简单，聪明的人大概一会儿就想出来了。

class NumArray {
    vector<int> sumArray;
public:
    NumArray(vector<int> &nums) {

        int temp=0;
        for(int i=0;i<nums.size();i++){
            temp+=nums[i];
            sumArray.push_back(temp);
        }
    }

    int sumRange(int i, int j) {
        int result;
        result=this->sumArray[j]-this->sumArray[i-1];
        return result;
    }
};


// Your NumArray object will be instantiated and called as such:
// NumArray numArray(nums);
// numArray.sumRange(0, 1);
// numArray.sumRange(1, 2);

 

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题外话：

最近状态有些不好，我事实上是一个常常状态不好的人，我【容易受环境干扰】、【理性感性参半】、【不容易坚守自己】

因为上述的缺点，常常陷入责怪自己的状态中，却不知道如何改变，最差却一直使用的解决办法就是明天再说，也许明天就好了。呸。