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#include #include #define MAX 10 #define EMPTY -1 struct stack { char data[MAX]; int top; }; int isempty(struct stack *s) { return (s->top == EMPTY) ? 1 : 0; } void emptystack(struct stack* s) { s->top=EMPTY; } void push(struct stack* s,int item) { if(s->top == (MAX-1)) { printf("\nSTACK FULL"); } else { ++s->top; s->data[s->top]=item; } } char pop(struct stack* s) { char ret=(char)EMPTY; if(!isempty(s)) { ret= s->data[s->top]; --s->top; } return ret; } void display(struct stack s) { while(s.top != EMPTY) { printf("\n%d",s.data[s.top]); s.top--; } } int isoperator(char e) { if(e == '+' || e == '-' || e == '*' || e == '/' || e == '%') return 1; else return 0; } int priority(char e) { int pri = 0; if(e == '*' || e == '/' || e =='%') pri = 2; else { if(e == '+' || e == '-') pri = 1; } return pri; } void infix2postfix(char* infix, char * postfix, int insertspace) { char *i,*p; struct stack X; char n1; emptystack(&X); i = &infix[0]; p = &postfix[0]; while(*i) { while(*i == ' ' || *i == '\t') { i++; } if( isdigit(*i) || isalpha(*i) ) { while( isdigit(*i) || isalpha(*i)) { *p = *i; p++; i++; } /*SPACE CODE*/ if(insertspace) { *p = ' '; p++; } /*END SPACE CODE*/ } if( *i == '(' ) { push(&X,*i); i++; } if( *i == ')') { n1 = pop(&X); while( n1 != '(' ) { *p = n1; p++; /*SPACE CODE*/ if(insertspace) { *p = ' '; p++; } /*END SPACE CODE*/ n1 = pop(&X); } i++; } if( isoperator(*i) ) { if(isempty(&X)) push(&X,*i); else { n1 = pop(&X); while(priority(n1) >= priority(*i)) { *p = n1; p++; /*SPACE CODE*/ if(insertspace) { *p = ' '; p++; } /*END SPACE CODE*/ n1 = pop(&X); } push(&X,n1); push(&X,*i); } i++; } } while(!isempty(&X)) { n1 = pop(&X); *p = n1; p++; /*SPACE CODE*/ if(insertspace) { *p = ' '; p++; } /*END SPACE CODE*/ } *p = '\0'; } int main() { char in[50],post[50]; strcpy(&post[0],""); printf("Enter Infix Expression : "); fflush(stdin); gets(in); infix2postfix(&in[0],&post[0],1); printf("Postfix Expression is : %s\n",&post[0]); return 0; } /* SAMPLE OUTPUT: Enter Infix Expression : A + B + C / (E - F) Postfix Expression is : A B + C E F - / + */ | ||||
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