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infix_postfix_stacks.c
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infix_postfix_stacks.c
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#include<stdio.h>
#include<ctype.h>
# define N 50
char stack[N];
int top=-1;
void push(char x){
top++;
stack[top]=x;
}
char pop(){
char x;
x=stack[top];
top--;
return x;
}
int isOperator(char ch){
if(ch=='+' || ch=='-' || ch=='*' || ch=='/'){
return 1;
}
else{
return 0;
}
}
int pri(char symbol){
if(symbol=='^'){
return 6;
}
else if(symbol=='*' || symbol=='/'){
return 3;
}
else if(symbol=='+' || symbol=='-'){
return 1;
}
else{
return 0;
}
}
int prs(char symbol){
if(symbol=='^'){
return 5;
}
else if(symbol=='*' || symbol=='/'){
return 4;
}
else if(symbol=='+' || symbol=='-'){
return 2;
}
else{
return 0;
}
}
int main(){
char infix[50],postfix[50],ch;
int i=0,k=0;
scanf("%s",infix);
push('#');
if((infix[1]=='+')&&(infix[2]=='+')){
printf("Not Valid Infix Expression");
}
else{
while((ch=infix[i])!='\0'){
if(ch=='('){
push(ch);
}
else if(isalnum(ch)){
postfix[k++]=ch;
}
else if(ch==')'){
while(stack[top]!='('){
postfix[k++]=pop();
}
ch=pop();
}
else{
while(pri(ch)<=prs(stack[top])){
postfix[k++]=pop();
}
push(ch);
}
i++;
}
}
while(stack[top]!='#'){
postfix[k++]=pop();
}
postfix[k]='\0';
printf("%s",postfix);
}