## Pat(A) 1102. Invert a Binary Tree (25)

### 1102. Invert a Binary Tree (25)

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

### 代码

#include "iostream"
#include "queue"
using namespace std;

int N;
int l[10];
int r[10];
int root;
bool isChild[10];

void init(){
cin>>N;
char c1,c2;
char c;
for(int i = 0; i < N; i++){
cin>>c1>>c2;
if(c1 >= '0' && c1 <= '9'){
l[i] = c1 - '0';
isChild[c1 - '0'] = true;
}else
l[i] = -1;
if(c2 >= '0' && c2 <= '9'){
r[i] = c2 - '0';
isChild[c2 - '0'] = true;
}else
r[i] = -1;
}
for(int i = 0; i < N; i++){
if(!isChild[i]){
root = i;
break;
}
}
}

void levelOrder(){
queue<int> que;
que.push(root);
bool first = true;
int x;
while(!que.empty()){
x = que.front();
que.pop();
if(first){
cout<<x;
first = false;
}else{
cout<<" "<<x;
}
if(r[x] != -1)
que.push(r[x]);
if(l[x] != -1)
que.push(l[x]);
}
cout<<endl;
}

void inOrder(int ro){
static bool first = true;
if(r[ro] != -1)
inOrder(r[ro]);
if(first){
cout<<ro;
first = false;
}else{
cout<<" "<<ro;
}
if(l[ro] != -1)
inOrder(l[ro]);
}

int main(){
init();
levelOrder();
inOrder(root);
cout<<endl;
system("pause");
}

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