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  • 7-3 Postfix Expression (25分)

    7-3 Postfix Expression (25分)
    Given a syntax tree (binary), you are supposed to output the corresponding postfix expression, with parentheses reflecting the precedences of the operators.

    Input Specification:
    Each input file contains one test case. For each case, the first line gives a positive integer N (≤ 20) which is the total number of nodes in the syntax tree. Then N lines follow, each gives the information of a node (the i-th line corresponds to the i-th node) in the format:

    data left_child right_child
    where data is a string of no more than 10 characters, left_child and right_child are the indices of this node's left and right children, respectively. The nodes are indexed from 1 to N. The NULL link is represented by −1. The figures 1 and 2 correspond to the samples 1 and 2, respectively.


    Output Specification:
    For each case, print in a line the postfix expression, with parentheses reflecting the precedences of the operators.There must be no space between any symbols.

    Sample Input 1:
    8

    • 8 7
      a -1 -1
    • 4 1
    • 2 5
      b -1 -1
      d -1 -1
    • -1 6
      c -1 -1
      Sample Output 1:
      (((a)(b)+)((c)(-(d))))
      Sample Input 2:
      8
      2.35 -1 -1
    • 6 1
    • -1 4
      % 7 8
    • 2 3
      a -1 -1
      str -1 -1
      871 -1 -1
      Sample Output 2:
      (((a)(2.35)*)(-((str)(871)%))+)
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  • 原文地址:https://www.cnblogs.com/houzm/p/13372475.html
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