LintCode-Maximum Subarray Difference

 1 public class Solution {
 2     /**
 3      * @param nums: A list of integers
 4      * @return: An integer indicate the value of maximum difference between two
 5      *          Subarrays
 6      */
 7     public int maxDiffSubArrays(ArrayList<Integer> nums) {
 8         int len = nums.size();
 9         if (len==0) return 0;
10 
11         int[] leftMin = new int[len];
12         int[] leftMax = new int[len];
13         int endMin = nums.get(0), endMax = nums.get(0);
14         leftMin[0] = endMin;
15         leftMax[0] = endMax;
16         for (int i=1;i<len;i++){
17             //Calculate max subarray.
18             endMax = Math.max(nums.get(i), nums.get(i)+endMax);
19             leftMax[i] = Math.max(leftMax[i-1],endMax);
20 
21             //Calculate min subarray.
22             endMin = Math.min(nums.get(i),nums.get(i)+endMin);
23             leftMin[i] = Math.min(leftMin[i-1],endMin);
24         }
25 
26         int[] rightMin = new int[len];
27         int[] rightMax = new int[len];
28         endMin = nums.get(len-1);
29         endMax = nums.get(len-1);
30         rightMin[len-1] = endMin;
31         rightMax[len-1] = endMax;
32         for (int i=len-2;i>=0;i--){
33             endMax = Math.max(nums.get(i),nums.get(i)+endMax);
34             rightMax[i] = Math.max(rightMax[i+1],endMax);
35             endMin = Math.min(nums.get(i),nums.get(i)+endMin);
36             rightMin[i] = Math.min(rightMin[i+1],endMin); 
37         }
38 
39         int maxDiff= 0;
40         for (int i=0;i<len-1;i++){
41             if (maxDiff<Math.abs(leftMin[i]-rightMax[i+1]))
42                 maxDiff = Math.abs(leftMin[i]-rightMax[i+1]);
43 
44             if (maxDiff<Math.abs(leftMax[i]-rightMin[i+1]))
45                 maxDiff = Math.abs(leftMax[i]-rightMin[i+1]);
46         }
47         return maxDiff;
48             
49 
50     }
51 }