【笔试记录】2020.8.22 猿辅导 - 服务器端开发（打印完全二叉树的边界）

牛客大佬的全ac代码

链接

打印完全二叉树的边界

根据结点序号位置，依次打印非叶子的左边界，非右边界的叶子结点，非左边界的右边界。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "limits.h"
#include "math.h"
using namespace std;

struct TreeNode{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x):val(x), left(NULL),right(NULL){}
};
int main(int argc, const char * argv[]) {
    vector<int> ledge; //非叶子的左边界：输入位置[0...n-1]中，符合2^n-1特点的结点
    vector<int> leaf;  //非右边界的叶子结点
    vector<int> redge; //非叶子非边界的右边界：输入位置[0...n-1]中，符合2^n-2特点的结点
    
    int n;
    cin >> n;
    int depth = (int)floor( log(n)/log(2) ); //log2(n)向下取整
    int nonleafNum, leafNum;
    //如果是满二叉树
    bool isman = false;
    if( (double)depth == (log(n)/log(2)) ){
        isman = true;
    }else{
        depth += 1;
    }nonleafNum = (int)pow(2, depth-1)-1; //非叶子结点个数：2^(depth-1)-1
    leafNum = n - nonleafNum; //叶子结点的个数
    
    //输入
    int tree[n];
    for(int i=0; i<n; i++){
        cin >> tree[i];
    }
//    cout << endl << "d:" << depth << " nonleafNum:" << nonleafNum << " leafNum:" << leafNum<< endl;
    //对于非叶子结点
    for(int i=0; i<nonleafNum; i++){
        //判断左边界
        if( ( (i+1)&i ) == 0 ){
            ledge.push_back(tree[i]);
        }else if( ( (i+2)&(i+1) ) == 0 ){ //判断右边界
            redge.push_back(tree[i]);
        }
    }
    //叶子结点
    for(int i=nonleafNum; i<n; i++){
        leaf.push_back(tree[i]);
    }
    //如果不是满二叉树，那在上一层中可能还剩了叶子结点
    //上一层中有孩子的结点的个数：(leafNum+1)/2，上一层的结点范围[2^(depth-2)-1, 2^(depth-1)-2]，注意除掉左右边界
    if( !isman ){
        
        int num = (leafNum+1)/2;
//        cout << "num:" << num;
        int l = (int)pow(2, depth-2);
        if( num >= 2 ){
            l = l + (num-1);
        }
        int r = (int)pow(2, depth-1)-3;
//        cout << " l:" << l << " r:" << r << endl;
        for(int i=l; i<=r; i++){
            leaf.push_back(tree[i]);
        }
    }
    for(int i=0; i<ledge.size(); i++){
        cout << ledge[i] << " ";
    }
    for(int i=0; i<leaf.size(); i++){
        cout << leaf[i] << " ";
    }
    for(int i=redge.size()-1; i>=0; i--){
        cout << redge[i] << " ";
    }
    cout << endl;
    return 0;
}

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