| #include<stdio.h> #include<string.h> #define LP 10 #define RP 20 #define OPERATOR 30 #define OPERAND 40 #define RPP 0 #define AP 1 #define SP 1 #define MP 2 #define DP 2 #define REMP 2 #define NONE 9 void InfixToPrefix(); int getType(char); int getPrecedence(char); void push(char); char pop(); char infix[50],stack[40],prefix[50]; int top; int main() { char ch; do { top=-1; printf(“Enter an Infix expression : “); gets(infix); strrev(infix); InfixToPrefix(); strrev(prefix); printf(“Prefix expression : %s\n”,prefix); printf(“Do you want to convert one more (y\\n) : “); ch=getche(); }while(ch==’y’); return 0; } void InfixToPrefix() { int i,p,l,type,prec; char next; i=p=0; l=strlen(infix); while(i<l) { type=getType(infix[i]); switch(type) { case RP: push(infix[i]); break; case LP: while((next=pop())!=’)’) { prefix[p]=next; ++p; } break; case OPERAND: prefix[p]=infix[i]; ++p; break; case OPERATOR: prec=getPrecedence(infix[i]); while((top>-1)&&(prec<getPrecedence(stack[top]))) { prefix[p]=pop(); ++p; } push(infix[i]); break; } ++i; } while(top>-1) { prefix[p]=pop(); ++p; } } int getType(char sym) { switch(sym) { case ‘(‘: return LP; case ‘)’: return RP; case ‘+’: case ‘-‘: case ‘*’: case ‘/’: case ‘%’: return OPERATOR; default: return OPERAND; } } int getPrecedence(char sym) { switch(sym) { case ‘)’: return RPP; case ‘+’: return AP; case ‘-‘: return SP; case ‘*’: return MP; case ‘/’: return DP; case ‘%’: return REMP; default: return NONE; } } void push(char sym) { ++top; stack[top]=sym; } char pop() { char sym; sym=stack[top]; –top; return sym; } |