【LeetCode-面試演算法經典-Java實現】【110-Balanced Binary Tree(平衡二叉樹)】
阿新 • • 發佈:2019-01-05
原題
Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
題目大意
給定一棵平衡二叉樹,判斷它是否是高度平衡的。一棵高度平衡的二叉樹是左右子樹的高度相差不超過1,對其左右子樹也是如此。
解題思路
遞迴分治法求解。
程式碼實現
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
演算法實現類
public class Solution {
private int minDepth = 0;
private int maxDepth = 0;
public boolean isBalanced(TreeNode root) {
if (root == null ) {
return true;
}
int left = depth(root.left);
int right = depth(root.right);
if (left - right > 1 || left - right < -1) {
return false;
} else {
return isBalanced(root.left) && isBalanced(root.right);
}
}
/**
* 求樹的高度
* @param n 樹的根結點
* @return 樹的高度
*/
private int depth(TreeNode n) {
if (n == null) {
return 0;
} if (n.left == null && n.right == null) {
return 1;
} else {
int left = depth(n.left);
int right = depth(n.right);
return 1 + (left > right ? left : right);
}
}
}
評測結果
點選圖片,滑鼠不釋放,拖動一段位置,釋放後在新的視窗中檢視完整圖片。