[leetcode] 303. Range Sum Query - Immutable

Posted 2020-10-15 zmj97

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.

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不是很懂这道题的意义....然后java写多了和cpp的语法有点混了。。忧伤。。。

 

我的代码：

class NumArray {
private: 
    vector<int> array;
public:
    NumArray(vector<int> nums) {
        for (int i = 0; i < nums.size(); i++) {
            nums[i] += nums[i-1];
            array.push_back(nums[i]);
        }
    }
    
    int sumRange(int i, int j) {
        if (i == 0) return array[j];
        else return array[j] - array[i-1];
    }
};

/**
 * Your NumArray object will be instantiated and called as such:
 * NumArray obj = new NumArray(nums);
 * int param_1 = obj.sumRange(i,j);
 */