二叉树的创建、遍历、翻转

BinaryTreeNode.h

//
//  BinaryTreeNode.h
//  BinaryTree
//
//  Created by KeSen on 15/9/7.
//  Copyright (c) 2015年 KeSen. All rights reserved.
//

#import <Foundation/Foundation.h>

@class BinaryTreeNode;

@interface BinaryTreeNode : NSObject

// 添加节点
+ (BinaryTreeNode *)addTree:(BinaryTreeNode *)p addValue:(id)value;

// 中序遍历
- (void)inOrderBinaryTree:(BinaryTreeNode *)p;

// 翻转
- (BinaryTreeNode *)invertTree:(BinaryTreeNode *)p;

@end

BinaryTreeNode.m

//
//  BinaryTreeNode.m
//  BinaryTree
//
//  Created by KeSen on 15/9/7.
//  Copyright (c) 2015年 KeSen. All rights reserved.
//

#import "BinaryTreeNode.h"

@implementation BinaryTreeNode
{
    id val;
    BinaryTreeNode *left;
    BinaryTreeNode *right;
}

// 添加节点
+ (BinaryTreeNode *)addTree:(BinaryTreeNode *)p addValue:(id)value {

    if (p == nil) {
        p = [[BinaryTreeNode alloc] init];
        p->val = value;
        p->left = nil;
        p->right = nil;

    } else if ([value integerValue] < [p->val integerValue]) {

        p->left = [BinaryTreeNode addTree:p->left addValue:value];
    } else {

        p->right = [BinaryTreeNode addTree:p->right addValue:value];
    }

    return p;
}

// 中序遍历二叉树
- (void)inOrderBinaryTree:(BinaryTreeNode *)p {

    if (p != nil) {
        [self inOrderBinaryTree:p->left];
        printf("%ld\n", (long)[p->val integerValue]);
        [self inOrderBinaryTree:p->right];
    }
}

- (BinaryTreeNode *)invertTree:(BinaryTreeNode *)p {

    if (p == nil) {
        return nil;
    }

    p->left = [p invertTree:p->left];
    p->right = [p invertTree:p->right];

    BinaryTreeNode *temp = p->left;
    p->left = p->right;
    p->right = temp;
    return p;
}

@end

main.m

//
//  main.m
//  BinaryTree
//
//  Created by KeSen on 15/9/7.
//  Copyright (c) 2015年 KeSen. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "BinaryTreeNode.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {

        BinaryTreeNode *root = nil;
        for (id value in @[@(2), @(5), @(6), @(8), @(9)]) {
            root = [BinaryTreeNode addTree:root addValue:value];
        }

        [root inOrderBinaryTree:root];

        printf("\n");

        BinaryTreeNode *invertTree = [root invertTree:root];
        [invertTree inOrderBinaryTree:invertTree];
    }
    return 0;
}

输出结果为：

2

5

6

8

9

9

8

6

5

2

github：https://github.com/action456789/BinaryTree

参考：http://blog.devtang.com/blog/2015/06/16/talk-about-tech-interview/

http://www.cocoachina.com/bbs/read.php?tid=177907