algorithm/[654]最大二叉树.java at master · Ada0910/algorithm

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//leetcode submit region begin(Prohibit modification and deletion)

/**

* Definition for a binary tree node.

* public class TreeNode {

* int val;

* TreeNode left;

* TreeNode right;

* TreeNode() {}

* TreeNode(int val) { this.val = val; }

* TreeNode(int val, TreeNode left, TreeNode right) {

* this.val = val;

* this.left = left;

* this.right = right;

* }

class Solution {

public TreeNode constructMaximumBinaryTree(int[] nums) {

return build(nums, 0, nums.length - 1);

}

// 这个函数的定义是：返回一个通过nums数组，以left,right构建的树的根节点

public TreeNode build(int[] nums, int left, int right) {

if (left > right) {

return null;

}

// 1.先找出数组的最大值

int maxValue = nums.length == 0 ? Integer.MIN_VALUE : nums[left];

int index = left;

// 这里的循环要以left，right作为边界

for (int i = left; i <= right; i++) {

if (maxValue < nums[i]) {

maxValue = nums[i];

index = i;

}

//2.以最大点的值构建二叉树

TreeNode root = new TreeNode(maxValue);

// 3.递归左子树

root.left = build(nums, left, index - 1);

// 4.递归右子树

root.right = build(nums, index + 1, right);

// 5.返回递归后的节点

return root;

}

//leetcode submit region end(Prohibit modification and deletion)

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