Algorithms_in_C 1.0.0
Set of algorithms implemented in C.
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infix_to_postfix.c File Reference

Infix to Postfix Expression Conversion More...

#include <stdio.h>
Include dependency graph for infix_to_postfix.c:

Data Structures

struct  Stack
 for printf() and scanf() More...
 

Functions

void push (struct Stack *p, char x)
 push function
 
char pop (struct Stack *p)
 pop function
 
int isOprnd (char ch)
 isOprnd function
 
int isEmpty (struct Stack s)
 isEmpty function
 
int getPrecedence (char op1, char op2)
 getPrecedence function returns the precedence after comparing two operators passed as parameter.
 
void convert (char infix[], char postfix[])
 convert function
 
int main ()
 main function
 

Detailed Description

Infix to Postfix Expression Conversion

Convert Infixed expressions to Postfix expression.

Author
Harsh Karande

Function Documentation

◆ convert()

void convert ( char  infix[],
char  postfix[] 
)

convert function

Parameters
infix[]: infix array provided by user
postfix[]: empty array to be given to convert()
Returns
postfixed expresion or \0 on exit
131{
132 struct Stack s; // initialze object reference of stack
133 s.tos = -1; // initalize the tos
134
135 int i, j = 0, pr;
136 char ch, temp;
137
138 for (i = 0; infix[i] != '\0'; i++)
139 {
140 ch = infix[i];
141
142 if (isOprnd(ch) == 1) // check if char is operand or operator
143 {
144 postfix[j] = ch; // assign ch to postfix array with index j
145 j++; // incement j
146 }
147 else
148 {
149 if (ch == '(')
150 {
151 push(&s, ch);
152 }
153 else
154 {
155 if (ch == ')')
156 {
157 while ((temp = pop(&s)) != '(')
158 {
159 postfix[j] = temp;
160 j++;
161 }
162 }
163 else
164 {
165 while (isEmpty(s) == 0) // check if stack is empty
166 {
167 pr = getPrecedence (ch,
168 s.arr[s.tos]); // check operator precedence
169
170 if (pr == 1)
171 {
172 break; // if ch has a greater precedence than
173 // s.arr[s.top]
174 }
175
176 postfix[j] = pop(&s);
177 j++;
178 }
179
180 push(&s, ch); // push ch to stack
181 }
182 }
183 }
184 }
185
186 while (isEmpty(s) == 0) // check if stack is empty
187 {
188 postfix[j] = pop(&s);
189 j++;
190 }
191
192 postfix[j] = '\0';
193}
char pop()
Function to pop from the stack.
Definition: infix_to_postfix2.c:45
uint16_t isEmpty()
Function to check whether the stack is empty or not.
Definition: infix_to_postfix2.c:61
void push(struct Stack *p, char ch)
push function
Definition: infix_to_postfix.c:55
int getPrecedence(char op1, char op2)
getPrecedence function returns the precedence after comparing two operators passed as parameter.
Definition: infix_to_postfix.c:201
int isOprnd(char ch)
isOprnd function
Definition: infix_to_postfix.c:93
for printf() and scanf()
Definition: infix_to_postfix.c:18
int tos
ā€¨static array of integers
Definition: infix_to_postfix.c:20
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◆ getPrecedence()

int getPrecedence ( char  op1,
char  op2 
)

getPrecedence function returns the precedence after comparing two operators passed as parameter.

Parameters
op1: first operator
op2: second operator
Returns
1 or 0 on exit
202{
203 if (op2 == '$')
204 {
205 return 0;
206 }
207 else if (op1 == '$')
208 {
209 return 1;
210 }
211 else if (op2 == '*' || op2 == '/' || op2 == '%')
212 {
213 return 0;
214 }
215 else if (op1 == '*' || op1 == '/' || op1 == '%')
216 {
217 return 1;
218 }
219 else if (op2 == '+' || op2 == '-')
220 {
221 return 0;
222 }
223 else
224 {
225 return 1;
226 }
227}

◆ isEmpty()

int isEmpty ( struct Stack  s)

isEmpty function

Parameters
s: it is the object reference of stack
Returns
1 or 0 on exit
113{
114 if (s.tos == -1) // check if stack is empty
115 {
116 return 1; // return for true result
117 }
118 else
119 {
120 return 0; // return for false result
121 }
122}

◆ isOprnd()

int isOprnd ( char  ch)

isOprnd function

Parameters
ch: this is the element from the infix array
Returns
1 or 0 on exit
94{
95 if ((ch >= 65 && ch <= 90) ||
96 (ch >= 97 && ch <= 122) || // check if ch is an operator or
97 (ch >= 48 && ch <= 57)) // operand using ASCII values
98 {
99 return 1; // return for true result
100 }
101 else
102 {
103 return 0; // return for false result
104 }
105}

◆ main()

int main ( void  )

main function

Returns
0 on exit
37{
38 char infix[20], postfix[20]; // initialize empty infix and postfix array
39
40 printf("Enter infix expression: "); // example : A+B-C*D/E$F
41 scanf("%s", infix); // get values for infix array
42
43 convert(infix, postfix);
44 printf("Postfix expression is %s", postfix); // output : AB+CD*EF$/-
45
46 return 0;
47}
void convert(char infix[], char postfix[])
convert function
Definition: infix_to_postfix.c:130
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◆ pop()

int pop ( struct Stack p)

pop function

Parameters
*p: used as a pointer variable of stack
Returns
x or \0 on exit
73{
74 char x;
75
76 if (p->tos == -1)
77 {
78 printf("Stack Underflow!");
79 return '\0';
80 }
81
82 x = p->arr[p->tos]; // assign the value of stack at index tos to x
83 p->tos -= 1; // decrement tos
84
85 return x;
86}

◆ push()

void push ( struct Stack p,
char  x 
)

push function

Parameters
*p: used as a pointer variable of stack
x: char to be pushed in stack
Returns
void
56{
57 if (p->tos == 9) // check if stack has reached its max limit
58 {
59 printf("Stack Overflow!");
60 return;
61 }
62
63 p->tos += 1; // increment tos
64 p->arr[p->tos] = x; // assign char x to index of stack pointed by tos
65}
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