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#include /*MACRO FUNCTION TO CHECK WHETHER GIVEN CHARACTER IS OPERAND OR NOT */ #define operand(x) (x>='a'&&x<='z' || x>='A'&&x<='Z' || x>='0'&&x<='9') char infix[30],prefix[30],stack[30]; int top,i=0; /* FUNCTION TO INITIALIZE THE STACK */ void init() { top=-1; } /* FUNCTION TO PUSH AN OPERATOR ON TO THE STACK */ void push(char x) { stack[++top]=x; } /* FUNCTION TO POP A CHARACTER STORED ONTO THE STACK */ char pop() { return(stack[top--]); } /* FUNCTION TO RETURN IN STACK PRIORITY OF A CHARACTER */ int isp(char x) { int y; y=(x=='('?6:x=='^'?4:x=='*'?2:x=='/'?2:x=='+'?1:x=='-'?1:x==')'?0:-1); return y; } /* FUNCTION TO RETURN INCOMING CHARACTER'S PRIORITY */ int icp(char x) { int y; y=(x=='('?6:x=='^'?4:x=='*'?2:x=='/'?2:x=='+'?1:x=='-'?1:x==')'?4:-1); return y; } /* FUNCTION TO CONVERT THE GIVEN INFIX TO PREFIX EXPRESSION */ void infixtoprefix() { int j,l=0; char x,y; stack[++top]='\0'; for (j=strlen(infix)-1; j>=0; j--) { x=infix[j]; if (operand(x)) prefix[l++]=x; else if (x=='(') while ((y=pop())!=')') prefix[l++]=y; else { while (isp(stack[top])>=icp(x)) prefix[l++]=pop(); push(x); } } while (top>=0) prefix[l++]=pop(); } /* MAIN PROGRAM */ int main() { init(); printf("Enter an infix expression :\n"); scanf("%s",infix); infixtoprefix(); strrev(prefix); printf("The resulting prefix expression is %s",prefix); return 0; } // End of main | ||||
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