989. Postfix to Prefix Conversion

You are given a valid postfix expression as a string, where:

  • Operands are single lowercase English letters ('a' to 'z')
  • Operators are binary: '+', '-', '*', '/'
  • The expression contains no spaces and is guaranteed to be valid.

Write a function to convert the postfix expression into a prefix expression, also as a string without spaces.

Example 1:

Input: expression = "ab+"

Output: "+ab"

Explanation: Postfix → Prefix

Example 2:

Input: expression = "abc*+d-"

Output: "-+a*bcd"

Now Your Turn!

Pick the correct output for the given input

Input: expression = "xyz*+ab/-"

Still unsure what the problem is asking ?

Let’s go through a few more examples, step by step, to make it clearer.

Constraints:

  • 1 <= len(postfix) <= 1000
  • The postfix expression is valid (no need to validate correctness)
  • Operands are lowercase letters (a-z)
  • Operators are binary: +, -, *, /
0
class Solution {
public:
string postToPre(string postfix) {
// Your code goes here
}
};
Test Case

Input:

Expression
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