Create Infix_to_Prefix_using_Stack.c

Infix_to_Prefix_using_Stack.c

@@ -0,0 +1,147 @@
+#include<stdio.h>
+#include<math.h>
+#include<string.h>
+#include <stdlib.h>
+#define MAX 20
+void push(int);
+char pop();
+void infix_to_prefix();
+int precedence (char);
+char stack[20],infix[20],prefix[20];
+int top = -1;
+
+int main()
+{
+printf("\nINPUT THE INFIX EXPRESSION : ");
+scanf("%s",infix);
+infix_to_prefix();
+return 0;
+}
+void push(int pos)
+{
+if(top == MAX-1)
+{
+printf("\nSTACK OVERFLOW\n");
+}
+else {
+top++;
+stack[top] = infix[pos];
+}}
+
+char pop()
+{
+char ch;
+if(top < 0)
+{
+printf("\nSTACK UNDERFLOW\n");
+exit(0);
+}
+else
+{
+ch = stack[top];
+stack[top] = '\0';
+top--;
+return(ch);
+}
+return 0;
+}
+void infix_to_prefix()
+{
+int i = 0,j = 0;
+strrev(infix);
+while(infix[i] != '\0')
+{
+if(infix[i] >= 'a' && infix[i] <= 'z')
+{
+prefix[j] = infix[i];
+j++;
+i++;
+}
+else if(infix[i] == ')' || infix[i] == '}' || infix[i] == ']')
+{
+push(i);
+i++;
+}
+else if(infix[i] == '(' || infix[i] == '{' || infix[i] == '[')
+{
+if(infix[i] == '(')
+{
+while(stack[top] != ')')
+{
+prefix[j] = pop();
+j++;
+}
+pop();
+i++;
+}
+else if(infix[i] == '[')
+{
+while(stack[top] != ']')
+{
+prefix[j] = pop();
+j++;
+}
+pop();
+i++;
+}
+else if(infix[i] == '{')
+{
+while(stack[top] != '}')
+{
+prefix[j] = pop();
+j++;
+}
+pop();
+i++;
+}}
+else
+{
+if(top == -1)
+{
+push(i);
+i++;
+}
+else if( precedence(infix[i]) < precedence(stack[top]))
+{
+prefix[j] = pop();
+j++;
+while(precedence(stack[top]) > precedence(infix[i])){
+prefix[j] = pop();
+j++;
+if(top < 0) {
+break;
+}}
+push(i);
+i++;
+}
+
+else if(precedence(infix[i]) >= precedence(stack[top]))
+{
+push(i);
+i++;
+}}}
+while(top != -1)
+{
+prefix[j] = pop();
+j++;
+}
+strrev(prefix);
+prefix[j] = '\0';
+printf("EQUIVALENT PREFIX NOTATION : %s ",prefix);
+}
+
+
+
+int precedence(char alpha)
+{
+if(alpha == '+' || alpha =='-')
+{
+return(1);
+}
+
+if(alpha == '*' || alpha =='/')
+{
+return(2);
+}
+return 0;
+}