| #include<stdio.h> #include<string.h> #include<stdlib.h> struct node { char c; struct node *left; struct node *right; }; struct node *stk[20], *temp, *root; char prefix[20],ch; int top=-1, max=20, len; void post(struct node*); void exptree(); void push(struct node*); struct node* pop(); int main() { printf(“Enter Prefix expression : “); scanf(“%s”, prefix); exptree(); printf(“Postfix expression is : “); post(root); return 0; } void post(struct node *p) { if(p != NULL) { post(p->left); post(p->right); printf(“%c”, p->c); } } void exptree() { int i; len = strlen(prefix); i=len-1; while(i>=0) { switch(prefix[i]) { case ‘+’ : case ‘-‘ : case ‘*’ : case ‘/’ : case ‘%’ : temp = (struct node*)malloc(sizeof(struct node)); temp->c = prefix[i]; temp->left = pop(); temp->right = pop(); push(temp); break; default : temp = (struct node*)malloc(sizeof(struct node)); temp->c = prefix[i]; temp->left = NULL; temp->right = NULL; push(temp); break; } –i; } root = pop(); } void push(struct node *p) { if(top==max) printf(“Stack is Full \n”); else stk[++top] = p; } struct node* pop() { if(top==-1) printf(“Invalid expression \n”); else return stk[top–]; } |