307. Range Sum Query - Mutable

標籤：color   numa   sum   for   res   new   query   ret   length   

 1 class NumArray { 2     int[] preSum; 3     int[] arr; 4     public NumArray(int[] nums) { 5         arr = nums; 6         preSum = new int[nums.length+1]; 7         preSum[0] = 0; 8         for(int i = 0; i < nums.length; i++){ 9             preSum[i+1] = preSum[i] + nums[i];10         }11         12     }13     14     public void update(int i, int val) {15         for(int j = i+1; j < preSum.length; j++){16             preSum[j] = preSum[j] - (arr[i]) + val;17         }18         arr[i] = val;19         20     }21     22     public int sumRange(int i, int j) {23         return preSum[j+1] - preSum[i];24         25     }26 }

 

307. Range Sum Query - Mutable