The following is from Max Howell @twitter:
Google: 90% of our engineers use the software you wrote (Homebrew), but you can't invert a binary tree on a whiteboard so fuck off.
Now it's your turn to prove that YOU CAN invert a binary tree!
Input Specification:
Each input file contains one test case. For each case, the first line gives a positive integer N (≤10) which is the total number of nodes in the tree -- and hence the nodes are numbered from 0 to N−1. Then N lines follow, each corresponds to a node from 0 to N−1, and gives the indices of the left and right children of the node. If the child does not exist, a - will be put at the position. Any pair of children are separated by a space.
Output Specification:
For each test case, print in the first line the level-order, and then in the second line the in-order traversal sequences of the inverted tree. There must be exactly one space between any adjacent numbers, and no extra space at the end of the line.
Sample Input:
8
1 -
- -
0 -
2 7
- -
- -
5 -
4 6
Sample Output:
3 7 2 6 4 0 5 1
6 5 7 4 3 2 0 1
1 #include <stdio.h> 2 #include <algorithm> 3 #include <set> 4 #include <string.h> 5 #include <vector> 6 #include <queue> 7 using namespace std; 8 struct node{ 9 int data; 10 int l=-1,r=-1; 11 }; 12 const int maxn = 11; 13 int n; 14 node tree[maxn]; 15 int vis[maxn]={0}; 16 void lvl(int root){ 17 queue<int> q; 18 q.push(root); 19 int cnt=0; 20 while(!q.empty()){ 21 int now=q.front(); 22 q.pop(); 23 cnt++; 24 if(cnt<n)printf("%d ",now); 25 else printf("%d ",now); 26 if(tree[now].r!=-1)q.push(tree[now].r); 27 if(tree[now].l!=-1)q.push(tree[now].l); 28 } 29 } 30 int cnt=0; 31 void ino(int root){ 32 if(root==-1)return; 33 if(tree[root].r!=-1) ino(tree[root].r); 34 cnt++; 35 if(cnt<n)printf("%d ",root); 36 else printf("%d",root); 37 if(tree[root].l!=-1) ino(tree[root].l); 38 } 39 int main(){ 40 scanf("%d",&n); 41 getchar(); 42 for(int i=0;i<n;i++){ 43 char c1,c2; 44 scanf("%c %c",&c1,&c2); 45 getchar(); 46 int l=-1,r=-1; 47 if(c1!='-'){ 48 l=c1-'0'; 49 vis[l]=1; 50 } 51 if(c2!='-'){ 52 r=c2-'0'; 53 vis[r]=1; 54 } 55 tree[i].l=l; 56 tree[i].r=r; 57 tree[i].data=i; 58 59 } 60 int root; 61 for(int i=0;i<n;i++){ 62 if(vis[i]==0){ 63 root=i; 64 break; 65 } 66 } 67 lvl(root); 68 ino(root); 69 }
注意点：又是读字符出现了错误，注意换行符一定要用getchar吃掉，不然会被%c认为是输入字符。别的就是普通的树的遍历