307. 区域和检索 - 数组可修改

 1 class NumArray 
 2 {
 3     vector<int> num;
 4 public:
 5     NumArray(vector<int>& nums) 
 6     {
 7         num = nums;
 8     }
 9     
10     void update(int i, int val) 
11     {
12         num[i] = val;
13     }
14     
15     int sumRange(int i, int j) 
16     {
17         int sum = 0;
18         for(int k = i;k <= j;k ++) sum += num[k];
19         return sum;
20     }
21 };