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Java [Leetcode 303]Range Sum Query - Immutable

时间:2016-02-18 23:03:38      阅读:277      评论:0      收藏:0      [点我收藏+]

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题目描述:

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.

解题思路:

如代码所示。

代码如下:

public class NumArray {
	int[] nums;

    public NumArray(int[] nums) {
        for(int i = 1; i < nums.length; i++){
        	nums[i] += nums[i - 1];
        }
        this.nums = nums;
    }

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

  

 

Java [Leetcode 303]Range Sum Query - Immutable

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原文地址:http://www.cnblogs.com/zihaowang/p/5199416.html

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