LeetCode1

##LeetCode303. Range Sum Query - Immutable
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.

题目的意思是给一个整形数组，计算在i和j之间的和

解答：

public class NumArray {
        int[] nums;
         public NumArray(int[] nums) {
            this.nums = nums;
        }

        public int sumRange(int i, int j) {

            if(nums==null || i<0 || j>=nums.length) {
                return 0;
            }
            int res = 0;
            for(int index = i;index<=j;index++) {
                res += nums[index];
            }
            return res;
        }
}