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  1. #include<iostream>
  2. #include<cstring>
  3. #include<stack>
  4. #include<vector>
  5. #include<cstdlib>
  6. #include<algorithm>
  7.  
  8. using namespace std;
  9.  
  10. int getWeight(char ch) {
  11.    switch (ch) {
  12.       case '/':
  13.       case '*': return 2;
  14.       case '+':
  15.       case '-': return 1;
  16.       default : return 0;
  17.    }
  18. }
  19. void infix_postfix(vector<char>& postfix)
  20. {
  21.     int i=0;
  22.     while(postfix.size()>1)
  23.     {
  24.         if(isdigit(postfix[i]))
  25.         {
  26.             i++;
  27.         }
  28.         else
  29.         {
  30.             switch(postfix[i])
  31.             {
  32.                 case '+':
  33.                 {
  34.                     postfix[i-2]=(postfix[i-2]-48)+ (postfix[i-1]-48)+48;
  35.                     postfix.erase(postfix.begin()+ i);
  36.                     postfix.erase(postfix.begin()+ i-1);
  37.                     break;
  38.                 }
  39.                 case '-':
  40.                 {
  41.                     postfix[i-2]=(postfix[i-2]-48)- (postfix[i-1]-48)+48;
  42.                     postfix.erase(postfix.begin()+ i);
  43.                     postfix.erase(postfix.begin()+ i-1);
  44.                     break;
  45.                 }
  46.                 case '*':
  47.                 {
  48.                     postfix[i-2]=(postfix[i-2]-48)* (postfix[i-1]-48)+48;
  49.                     postfix.erase(postfix.begin()+ i);
  50.                     postfix.erase(postfix.begin()+ i-1);
  51.                     break;
  52.                 }
  53.                 case '/':
  54.                 {
  55.                     postfix[i-2]=(postfix[i-2]-48)/ (postfix[i-1]-48)+48;
  56.                     postfix.erase(postfix.begin()+ i);
  57.                     postfix.erase(postfix.begin()+ i-1);
  58.                     break;
  59.                 }
  60.             }
  61.             i=i-1;
  62.         }
  63.     }
  64. }
  65. void infix2postfix(char infix[], vector<char>& postfix, int size) {
  66.    stack<char> s;
  67.    int weight;
  68.    int i = 0;
  69.    int k = 0;
  70.    char ch;
  71.    while (i < size) 
  72.    {
  73.       ch = infix[i];
  74.       if (ch == '(')
  75.       {
  76.          s.push(ch);
  77.          i++;
  78.          continue;
  79.       }
  80.       if (ch == ')') 
  81.       {
  82.          while (!s.empty() && s.top() != '(')
  83.          {
  84.            // postfix[k++] = s.top();
  85.           postfix.push_back(s.top());
  86.             s.pop();
  87.          }
  88.          if (!s.empty())
  89.          {
  90.             s.pop();
  91.  
  92.          }
  93.          i++;
  94.          continue;
  95.  
  96.       }
  97.       weight = getWeight(ch);
  98.       if (weight == 0)
  99.       {
  100.         // postfix[k++] = ch;
  101.         postfix.push_back(ch);
  102.  
  103.       }
  104.       else 
  105.       {
  106.          if (s.empty())
  107.          {
  108.             s.push(ch); 
  109.  
  110.          }
  111.          else
  112.          {
  113.             while (!s.empty() && s.top() != '(' &&
  114.                   weight <= getWeight(s.top()))
  115.                   {
  116.                //postfix[k++] = s.top();
  117.                postfix.push_back(s.top());
  118.                s.pop(); 
  119.  
  120.                   }
  121.             s.push(ch);
  122.          }
  123.  
  124.       }
  125.       i++;
  126.  
  127.    }
  128.    while (!s.empty()) {
  129.       //postfix[k++] = s.top();
  130.       postfix.push_back(s.top());
  131.       s.pop();
  132.    }
  133.   // postfix[k] = 0;
  134. }
  135. int main() {
  136.    char infix[] = "9*5*4-(8-4/2)";
  137.    int size = strlen(infix);
  138.   // char postfix[size];
  139.   vector<char>postfix;
  140.    infix2postfix(infix,postfix, size);
  141.    cout<<"\nInfix Expression :: "<<infix;
  142.    cout<<"\nPostfix Expression :: ";
  143.    for(int i=0;i<postfix.size();i++)
  144.    cout<<postfix[i];
  145.    infix_postfix(postfix);
  146.   cout<<"\nanswer="<<(int)postfix[0];
  147.   //cout<<endl<<postfix.size()<<endl;
  148.    return 0;
  149.  
  150.    }
Success #stdin #stdout 0s 16056KB
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stdin
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Standard input is empty
stdout
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Infix Expression :: 9*5*4-(8-4/2)
Postfix Expression :: 95*4*842/--
answer=-34
https://ideone.com/BqexU5
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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