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Commit 4be19d7

Browse files
fixed the bug
1 parent 62abce2 commit 4be19d7

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1 file changed

+66
-86
lines changed

1 file changed

+66
-86
lines changed
Lines changed: 66 additions & 86 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,5 @@
11
#include<iostream>
22
#include<stack>
3-
#include<algorithm>
43
using namespace std;
54

65
/*Algorithm-
@@ -11,7 +10,7 @@ using namespace std;
1110

1211
bool isOperator(char c)
1312
{
14-
return (!isdigit(c) && isalpha(c));
13+
return (!isdigit(c) && !isalpha(c));
1514
}
1615

1716
int getPriority(char c)
@@ -27,95 +26,76 @@ int getPriority(char c)
2726
return 0;
2827
}
2928

30-
string infixToPostfix(string infix)
31-
{
32-
33-
int l = infix.size();
34-
stack<char> char_stack;
35-
string output;
36-
37-
for (int i = 0; i < l; i++) {
38-
39-
// If the scanned character is an
40-
// operand, add it to output.
41-
if (isalpha(infix[i]) || isdigit(infix[i]))
42-
output += infix[i];
43-
44-
// If the scanned character is an
45-
// ‘(‘, push it to the stack.
46-
else if (infix[i] == '(')
47-
char_stack.push('(');
48-
49-
// If the scanned character is an
50-
// ‘)’, pop and output from the stack
51-
// until an ‘(‘ is encountered.
52-
else if (infix[i] == ')') {
53-
54-
while (char_stack.top() != '(') {
55-
output += char_stack.top();
56-
char_stack.pop();
57-
}
58-
59-
// Remove '(' from the stack
60-
char_stack.pop();
61-
}
62-
63-
// Operator found
64-
else {
65-
66-
if (isOperator(char_stack.top())) {
67-
while (getPriority(infix[i])
68-
<= getPriority(char_stack.top())) {
69-
output += char_stack.top();
70-
char_stack.pop();
71-
}
72-
73-
// Push current Operator on stack
74-
char_stack.push(infix[i]);
75-
}
76-
}
77-
}
78-
return output;
79-
}
80-
81-
8229

83-
84-
string infixToPrefix(string infix)
30+
string InfixToPostfix(string infix)
8531
{
86-
/* Reverse String
87-
* Replace ( with ) and vice versa
88-
* Get Postfix
89-
* Reverse Postfix * */
90-
int l = infix.size();
91-
92-
// Reverse infix
93-
reverse(infix.begin(), infix.end());
94-
95-
// Replace ( with ) and vice versa
96-
for (int i = 0; i < l; i++) {
97-
98-
if (infix[i] == '(') {
99-
infix[i] = ')';
100-
i++;
101-
}
102-
else if (infix[i] == ')') {
103-
infix[i] = '(';
104-
i++;
105-
}
106-
}
107-
108-
string prefix = infixToPostfix(infix);
109-
110-
// Reverse postfix
111-
reverse(prefix.begin(), prefix.end());
112-
113-
return prefix;
32+
infix = '(' + infix + ')';
33+
int len = infix.size();
34+
string output;
35+
36+
stack<char>s;
37+
38+
for(int i = 0 ; i < len; i++)
39+
{
40+
//if operand-add it to the postfix expression
41+
if(isalpha(infix[i]) || isdigit(infix[i]))
42+
output += infix[i];
43+
44+
//if opening brace then push it to stack
45+
else if(infix[i]=='(')
46+
s.push(infix[i]);
47+
48+
else if(infix[i]==')')
49+
{
50+
while(!s.empty() && s.top() != '(')
51+
{
52+
output += s.top();
53+
s.pop();
54+
}
55+
56+
//remove ( from stack
57+
s.pop();
58+
}
59+
60+
//if operator is found
61+
else
62+
{
63+
64+
if(isOperator(infix[i]))
65+
{
66+
while(!s.empty() && getPriority(infix[i]) <= getPriority(s.top()))
67+
{
68+
output += s.top();
69+
s.pop();
70+
}
71+
72+
//push current lower priority operator on stack
73+
s.push(infix[i]);
74+
75+
}
76+
}
77+
78+
}
79+
80+
81+
//if remaining elements in stack, make it empty
82+
while(!s.empty())
83+
{
84+
output += s.top();
85+
s.pop();
86+
}
87+
88+
89+
90+
return output;
91+
11492
}
11593

94+
95+
11696
int main()
11797
{
118-
string s = "(A*B+C/D)";
119-
cout<<infixToPostfix(s);
98+
string s= InfixToPostfix("(a-b/c)*(a/k-l)");
99+
cout<<s;
120100
return 0;
121101
}

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