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Given an integer array with no duplicates. A max tree building on this array is defined as follow:
Construct the max tree by the given array.
Example
Given [2, 5, 6, 0, 3, 1], the max tree constructed by this array is:
6
/ 5 3
/ / 2 0 1
采用递归的解法会Stack Overflow. 因此尝试非递归解法。
先给出递归解法。
1 /** 2 * Definition of TreeNode: 3 * public class TreeNode { 4 * public int val; 5 * public TreeNode left, right; 6 * public TreeNode(int val) { 7 * this.val = val; 8 * this.left = this.right = null; 9 * } 10 * } 11 */ 12 public class Solution { 13 /** 14 * @param A: Given an integer array with no duplicates. 15 * @return: The root of max tree. 16 */ 17 public TreeNode maxTree(int[] A) { 18 if (A == null || A.length == 0) { 19 return null; 20 } 21 return helper(A, 0, A.length - 1); 22 } 23 24 private int findMax(int[] A, int left, int right) { 25 int max = Integer.MIN_VALUE; 26 int ans = -1; 27 for (int i = left; i <= right; i++) { 28 if (max < A[i]) { 29 ans = i; 30 max = A[i]; 31 } 32 } 33 return ans; 34 } 35 36 private TreeNode helper(int[] A, int left, int right) { 37 if (left > right) { 38 return null; 39 } 40 int position = findMax(A, left, right); 41 TreeNode root = new TreeNode(A[position]); 42 root.left = helper(A, left, position - 1); 43 root.right = helper(A, position + 1, right); 44 return root; 45 } 46 }
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原文地址：http://www.cnblogs.com/FLAGyuri/p/5445059.html
