ExpressionTreeRE4.c

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*   Created by B I                                                                         *
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#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <stdbool.h>
typedef struct node{
    bool x;
    int value;
    char data;
    struct node *lp;
    struct node *rp;
}* Node;
int ip(char x);
Node Tree(char pf[]);
int answer(Node root);
int Valid(Node root);
int main(void) {
    char in[20];
    Node ExpTree = NULL;    
    int ans;
    printf("Enter the valid expression:\n");
    scanf("%s",in);
    ExpTree = Tree(in);
    ans = answer(ExpTree);
    printf("The Answer is %d\n",ans);
    return 0;
}
int ip(char x){
if(x == '(' || x == '#' )
 return 0;
 else if (x == '+' || x == '-')
 return 1;
 else if (x == '*' || x == '/')
 return 2;
 else if (x =='$' || x == '^' )
 return 3;
 else
 printf(" %c was to be tested\n",x);
 exit(0);
 }

Node Tree(char in[]){
Node DigStk[10],OpStk[10];
int j=0,topD=-1,topO= 0;
OpStk[0] = (Node)malloc(sizeof(struct node));
OpStk[0]->data = '#';
while(in[j]!='\0'){
Node temp = NULL;
temp = (Node)malloc(sizeof(struct node));
temp->data = in[j++];
temp->lp = NULL;
temp->rp = NULL;
if(temp->data =='-' && ( j<2 || (!isdigit(in[j-2]) && in[j-2] != ')'))){
    temp->x = 1;
    temp->value = 0;
        while(isdigit(in[j]))
    temp->value = temp->value*10 - (int)in[j++] + 48;
    DigStk[++topD] = temp; 
    
}
else if(isdigit(temp->data)){
    temp->x = 1;
    temp->value = (int)temp->data - 48;
    while(isdigit(in[j]))
    temp->value = temp->value*10 + (int)in[j++]-48;
    DigStk[++topD] = temp; 
}
else{
    temp->x = 0;
     if (temp->data=='(')
          OpStk[++topO]=temp;
        else if (temp->data==')'){
            while (OpStk[topO]->data!='(') {
            OpStk[topO]->rp = DigStk[topD--];
            OpStk[topO]->lp = DigStk[topD];
            DigStk[topD] = OpStk[topO--];
            }
            free(temp);
            free(OpStk[topO--]);
        }
        else{
            if(ip(OpStk[topO]->data) < ip(temp->data))
                OpStk[++topO] = temp;
            else{
                while (ip(OpStk[topO]->data) >= ip(temp->data)) {
            OpStk[topO]->rp = DigStk[topD--];
            OpStk[topO]->lp = DigStk[topD];
            DigStk[topD] = OpStk[topO--];
                }
            OpStk[++topO] = temp;  
            }
        }
    }
}
while (OpStk[topO]->data!='#')
{
                OpStk[topO]->rp = DigStk[topD--];
            OpStk[topO]->lp = DigStk[topD];
            DigStk[topD] = OpStk[topO--];
      }
return DigStk[topD];
}
int answer(Node root){
if(root->x)
return root->value;
else 
   switch(root->data)     
   {
      case '+':  return (answer(root->lp)+answer(root->rp));
      case '-':  return (answer(root->lp)-answer(root->rp));
      case '*':  return (answer(root->lp)*answer(root->rp));
      case '/':  return (answer(root->lp)/answer(root->rp));
      case '^':     
      case '$':  return ((int)pow((double)answer(root->lp),(double)answer(root->rp)));
      default: return 0;
   }
}