Created
March 1, 2016 19:39
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Converts a simple infix expression string into postfix expression by using stack
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#include <stdio.h> | |
#include <stdlib.h> | |
struct node | |
{ | |
int num; | |
struct node *link; | |
}*top; | |
int check(char c); | |
void insert(char c); | |
void push(char c,int value); | |
void pop(); | |
char printVal(int value); | |
int j; | |
char b[7]; | |
int main() | |
{ | |
int i,value; | |
char a[7]={'a','*','b','+','c','/','e'}; | |
j=0; | |
for(i=0;i<7;i++) | |
{ | |
value=check(a[i]); | |
if(value==0) | |
insert(a[i]); | |
else | |
push(a[i],value); | |
} | |
while(top!=NULL) | |
pop(); | |
for(i=0;i<7;i++) | |
printf("%c ",b[i]); | |
return 0; | |
} | |
int check(char c) | |
{ | |
if(c=='+') | |
return 1; | |
if(c=='-') | |
return 2; | |
if(c=='*') | |
return 3; | |
if(c=='/') | |
return 4; | |
else | |
return 0; | |
} | |
void insert(char c) | |
{ | |
b[j]=c; | |
j++; | |
} | |
void push(char c,int value) | |
{ | |
struct node *temp=((struct node *)malloc(sizeof(struct node))); | |
temp->num=value; | |
if(top==NULL) | |
{ | |
top=temp; | |
temp->link=NULL; | |
} | |
else | |
{ | |
if(value==4) | |
{ | |
while(top!=NULL && (top->num==3||top->num==4)) | |
pop(); | |
temp->link=top; | |
top=temp; | |
return; | |
} | |
if(value==3) | |
{ | |
while(top!=NULL && (top->num==3||top->num==4)) | |
pop(); | |
temp->link=top; | |
top=temp; | |
return; | |
} | |
if(value==2) | |
{ | |
while(top!=NULL && (top->num==2||top->num==1||top->num==3||top->num==4)) | |
pop(); | |
temp->link=top; | |
top=temp; | |
return; | |
} | |
if(value==1) | |
{ | |
while(top!=NULL && (top->num==2||top->num==1||top->num==3||top->num==4)) | |
pop(); | |
temp->link=top; | |
top=temp; | |
return; | |
} | |
} | |
} | |
void pop() | |
{ | |
char ch=printVal(top->num); | |
insert(ch); | |
struct node *ptr=top; | |
top=top->link; | |
free(ptr); | |
} | |
char printVal(int value) | |
{ | |
if(value==1) | |
return '+'; | |
if(value==2) | |
return '-'; | |
if(value==3) | |
return '*'; | |
if(value==4) | |
return '/'; | |
} |
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