65 lines
1.7 KiB
C++
65 lines
1.7 KiB
C++
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// Program to convert a prefix expression to postfix expression
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// Prefix expression : An expression in which the operator appears before the operands.
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// Postfix expression : An expression in which the operator appears after the operands.
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// Alogorithm
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// To convert prefix to postfix expression we follow steps given below:
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// Step 1. If the symbol is an operand, push it to the stack
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// Step 2. If symbol is an operator then pop top two elements from stack
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// Step 3. Then push an expression by concatenating (+op1+op2+symbol)
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// Step 4. At last return the top element of stack as postfix expression
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// CODE:
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#include<bits/stdc++.h>
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using namespace std;
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// Function to convert prefix to postfix expression
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string prefix_to_postfix(string prefix)
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{
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stack<string> s;
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// length of prefix expression
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int l=prefix.length();
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// Iterating through the Prefix expression from right to left
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for(int i=l-1;i>=0;i--){
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// if the symbol is an operand, push it to the stack
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if(prefix[i]>='a' && prefix[i]<='z'||prefix[i]>='A' && prefix[i]<='Z'){
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s.push(string(1,prefix[i]));
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}
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// if symbol is an operator
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else
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{
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string op1=s.top();
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s.pop();
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string op2=s.top();
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s.pop();
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string temp=(op1+op2+prefix[i]);
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s.push(temp);
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}
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}
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// returning element at top of stack
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return s.top();
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}
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// MAIN FUNCTION
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int main()
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{
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string exp;
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cout<<"Enter expression: ";
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cin>>exp;
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cout<<"Prefix to Postfix expression is: "<<prefix_to_postfix(exp);
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}
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// OUTPUT:
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// Enter expression: *-a/bc-/akl
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// Prefix to Postfix expression is: abc/-ak/l-*
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