Lintcode: Minimum Subarray 解题报告

Minimum Subarray

原题链接： http://lintcode.com/zh-cn/problem/minimum-subarray/#

Given an array of integers, find the subarray with smallest sum.

Return the sum of the subarray.

注意

The subarray should contain at least one integer.

样例

For [1, -1, -2, 1], return -3

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SOLUTION 1：

1. 我们把整个array * -1，把它转化为求最大和的题目。

2. 然后我们可以使用Sliding window的方法来做。记录一个sum，如果发现sum<0 则丢弃，否则不断把当前的值累加到sum，

3. 每计算一次sum,求一次max.

4. 返回-max即可。

 1 public class Solution {

 2     /**

 3      * @param nums: a list of integers

 4      * @return: A integer indicate the sum of minimum subarray

 5      */

 6     public int minSubArray(ArrayList<Integer> nums) {

 7         // write your code

 8         

 9         int len = nums.size();

10         

11         int max = Integer.MIN_VALUE;

12         int sum = 0;

13         for (int i = 0; i < len; i++) {

14             if (sum < 0) {

15                 sum = -nums.get(i);

16             } else {

17                 sum += -nums.get(i);

18             }

19             

20             max = Math.max(max, sum);

21         }

22         

23         return -max;

24     }

25 }

View Code

GITHUB:

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