标签：advance pat dfs
An inorder binary tree traversal can be implemented in a non-recursive way with a stack. For example, suppose that when a 6-node binary tree (with the keys numbered from 1 to 6) is traversed, the stack operations are: push(1); push(2); push(3); pop(); pop(); push(4); pop(); pop(); push(5); push(6); pop(); pop(). Then a unique binary tree (shown in Figure 1) can be generated from this sequence of operations. Your task is to give the postorder traversal sequence of this tree.
Input Specification:
Each input file contains one test case. For each case, the first line contains a positive integer N (<=30) which is the total number of nodes in a tree (and hence the nodes are numbered from 1 to N). Then 2N lines follow, each describes a stack operation in the format: "Push X" where X is the index of the node being pushed onto the stack; or "Pop" meaning to pop one node from the stack.
Output Specification:
For each test case, print the postorder traversal sequence of the corresponding tree in one line. A solution is guaranteed to exist. All the numbers must be separated by exactly one space, and there must be no extra space at the end of the line.
Sample Input:6 Push 1 Push 2 Push 3 Pop Pop Push 4 Pop Pop Push 5 Push 6 Pop PopSample Output:
3 4 2 6 5 1
#include<cstdio>
#include<cstdlib>
#include<algorithm>
using namespace std;
char op[10];
int val,n,iter=0;
bool flag;
struct TreeNode{
int num;
TreeNode *left;
TreeNode *right;
TreeNode(int num):num(num),left(NULL),right(NULL){}
~TreeNode();
};
TreeNode* buildTree(){
if(iter>=n)
return NULL;
scanf("%s",op);
TreeNode *root=NULL;
if(op[1]=='u'){
scanf("%d",&val);
root=new TreeNode(val);
++iter;
root->left=buildTree();
++iter;
root->right=buildTree();
}
return root;
}
void DFS(TreeNode *root){
if(root==NULL)
return;
DFS(root->left);
DFS(root->right);
if(flag){
printf("%d",root->num);
flag=false;
}else{
printf(" %d",root->num);
}
}
int main(int argc,char *argv[]){
scanf("%d",&n);
n=n*2;
TreeNode *root=buildTree();
flag=true;
DFS(root);
printf("\n");
return 0;
}
Pat(Advanced Level)Practice--1086(Tree Traversals Again)
标签：advance pat dfs
原文地址：http://blog.csdn.net/cstopcoder/article/details/42566737
