RangeSumQuery.java

/*
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:
You may assume that the array does not change.
There are many calls to sumRange function.
*/

public class NumArray {
 public static int[] f = new int[10000];
 public NumArray(int[] nums) {
 int sum = 0;
 for (int i = 0; i < nums.length; i++) {
 sum += nums[i];
 f[i] = sum;
 }
 }

 public int sumRange(int i, int j) {
 if (i == 0) return f[j];
 return f[j] - f[i - 1]; 
 }
}


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