PAT_A1086#Tree Traversals Again
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Description:
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.
Figure 1
Input Specification:
Each input file contains one test case. For each case, the first line contains a positive integer N (≤) which is the total number of nodes in a tree (and hence the nodes are numbered from 1 to N). Then 2 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 Pop
Sample Output:
3 4 2 6 5 1
Keys:
Code:
1 /* 2 time: 2019-06-30 14:34:48 3 problem: PAT_A1086#Tree Traversals Again 4 AC: 24:16 5 6 题目大意: 7 给出中序遍历的出栈和入栈操作,打印后序遍历 8 9 基本思路: 10 模拟二叉树的遍历过程,Push就是存在子树,Pop就是空子树 11 */ 12 #include<cstdio> 13 #include<string> 14 #include<iostream> 15 using namespace std; 16 int n; 17 18 void InOrder() 19 20 string op; 21 int data; 22 cin >> op; 23 if(op == "Push") 24 scanf("%d", &data); 25 else 26 return; 27 static int pt=0; 28 InOrder(); 29 InOrder(); 30 printf("%d%c", data, ++pt==n?‘\\n‘:‘ ‘); 31 32 33 int main() 34 35 #ifdef ONLINE_JUDGE 36 #else 37 freopen("Test.txt", "r", stdin); 38 #endif // ONLINE_JUDGE 39 40 scanf("%d", &n); 41 InOrder(); 42 43 return 0; 44
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