Create 16_rangeSumQuery.cpp

Author: FazeelUsmani

08 August Leetcode Challenge 2021/16_rangeSumQuery.cpp

@@ -0,0 +1,14 @@
+class NumArray { // 12 ms, faster than 99.87%
+public:
+ vector<int>& preSum; // `preSum` will reference to `nums` array, no copy at all!
+ 
+ NumArray(vector<int>& nums) : preSum(nums) {
+ for (int i = 1; i < preSum.size(); ++i)
+ preSum[i] += preSum[i-1]; 
+ }
+ 
+ int sumRange(int left, int right) {
+ if (left == 0) return preSum[right];
+ return preSum[right] - preSum[left-1];
+ }
+};