LeetCode -- Range Sum Query

Posted 2020-06-13

geQuestion:

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:

1. You may assume that the array does not change.
2. There are many calls to sumRange function.

 

Analysis:

给出一个整数数组，得出i与j之间的数字之和（i<=j）。你可以假设数组不会改变，并且他们可以调用多次sunRange函数。

 

Answer：

public class NumArray {
    int[] num;
    public NumArray(int[] nums) {
        this.num = nums;
    }
    public int sumRange(int i, int j) {
        int res = 0;
        for(int k=i; k<j+1; k++) {
            res += num[k];
        }
        return res;
    }
    
}


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