Lintcode:subarray Sum Problem Solving report

Subarray Sum

Original title Link: http://lintcode.com/zh-cn/problem/subarray-sum/#

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 last number of the index.

Sample Example

Given [ -3, 1, 2, -3, 4], return [0, 2] or [1, 3].

label Expand

Solution 1:

We have an O (N) solution. Use map to record the value of index, sum. When the sum of two index is encountered at the same time, the representation from index1+1 to Index2 is a solution.

Note: Add an index =-1 as the virtual node. So that we can record the solution of index1 = 0.

Space complexity: O (N)

1  Public classSolution {2     /**3      * @paramnums:a List of integers4      * @return: A list of integers includes the index of the first number5 * The index of the last number6      */7      PublicArraylist<integer> Subarraysum (int[] nums) {8         //Write your code here9         Ten         intLen =nums.length; One          Aarraylist<integer> ret =NewArraylist<integer>(); -          -Hashmap<integer, integer> map =NewHashmap<integer, integer>(); the          -         //We Set the index-1 sum to being 0 to let us more convient to count. -Map.put (0,-1); -          +         intsum = 0; -          for(inti = 0; i < Len; i++) { +Sum + =Nums[i]; A              at             if(Map.containskey (sum)) { -                 //For Example: -                 //-3 1 2-3 4 -                 //sum:0 -3-2 0-3 1 -                 //Then we got the solution is:0-2 -Ret.add (Map.get (sum) + 1); in Ret.add (i); -                 returnret; to             } +              -             //Store the Key:value of Sum:index. the map.put (sum, i); *         } $         Panax Notoginseng         returnret; -     } the}

View Code

GITHUB:

Https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/lintcode/array/SubarraySum.java

Lintcode:subarray Sum Problem Solving report