LintCode Subarray Sum

最新推荐文章于 2019-01-26 07:40:56 发布

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最新推荐文章于 2019-01-26 07:40:56 发布

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本文介绍了一种解决子数组求和为零问题的方法。给定一个整数数组，找到其中一个子数组，使得该子数组内元素之和为零，并返回该子数组的起始和结束索引。

description：
Given an integer array, find a subarray where the sum of numbers is zero. Your code should return the index of the first number and the index of the last number.

Notice

There is at least one subarray that it’s sum equals to zero.

Have you met this question in a real interview? Yes
Example
Given [-3, 1, 2, -3, 4], return [0, 2] or [1, 3].

题目非常简单

public class Solution {
    /**
     * @param nums: A list of integers
     * @return: A list of integers includes the index of the first number 
     *          and the index of the last number
     */
    public ArrayList<Integer> subarraySum(int[] nums) {
        // write your code here
        if (nums == null || nums.length == 0) {
            return null;
        }
        ArrayList<Integer> list = new ArrayList<>();
        Map<Integer, Integer> map = new HashMap<>();
        map.put(0, 0);
        int sum = 0;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (map.containsKey(sum)) {
                if (sum == 0) {
                    list.add(map.get(sum));
                    list.add(i);
                } else {
                    list.add(map.get(sum) + 1);
                    list.add(i);
                }
                break;
            } else {
                map.put(sum, i);
            }
        }
        return list;
    }
}