c program for Expression Tree

#include<iostream.h> #include<string.h> #include<alloc.h> #include<conio.h> union info {   int x;   char ch; }; struct tree {   char data;   union info data2;   struct tree *left,*right; }h; char exp[20]; int n; int check_precedency(char ch) {   switch(ch)   {     case '+':     case '-':     return 1;     case '*':     case '/':     return 2;     default:     return 3;   } } int detect(char ch) {   switch(ch)   {     case '+':     case '-':     case '*':     case '/':     return 1;     default:     return 0;   } } int convert(char ch) {   switch(ch)   {     case '1':     return 1;     case '2':     return 2;     case '3':     return 3;     case '4':     return 4;     case '5':     return 5;     case '6':     return 6;     case '7':     return 7;     case '8':     return 8;     case '9':     return 9;     default:     return 0;   } } int convertCharToInt(char exp[],int l,int u) {  char s[10];  int k=0;  for(int i=l;i<u;i++,k++)  {   s[k]=exp[i];  }  s[k]='\0';  float x=strtod(s,) } void Exp_tree(tree*q,int lb,int ub) {  if(lb>ub)return;  if(lb>=ub)  {  q->data=exp[lb];  q->data2.x=convert(exp[lb]);  q->right=NULL;  q->left=NULL;  return;  }  int previous=4,precedency,position;  for(int i=ub;i>=lb;i-- )  {    precedency=check_precedency(exp[i]);    if(previous>precedency)    {position=i;previous=precedency;}  }   i=position;   q->data2.ch=exp[i];   q->data=exp[i];   q->left=(tree*)malloc(sizeof(tree));   Exp_tree(q->left,lb,i-1);   q->right=(tree*)malloc(sizeof(tree));   Exp_tree(q->right,i+1,ub); } int evaluate(tree* q) {   switch(q->data2.ch)   {     case '+':       return(q->left->data2.x+q->right->data2.x);     case '-':       return(q->left->data2.x-q->right->data2.x);     case '*':       return(q->left->data2.x*q->right->data2.x);     case '/':       return(q->left->data2.x/q->right->data2.x);   } } void find(tree *q) {   if(q->left==NULL||q->right==NULL)return;   find(q->left);   find(q->right);   if(q->left->right==NULL&&q->left->left==NULL&&q->right->right==NULL&&q->right->left==NULL)   {    cout<<"\nLeaf Node.: "<<q->left->data2.x<<" "<<q->right->data2.x;    q->data2.x=evaluate(q);    cout<<"\tOperator.: "<<q->data<<"Result.: "<<q->data2.x;    q->left=NULL;    q->right=NULL;   } } void print_inorder(struct tree *p) {      if(p==NULL)return;      print_inorder(p->left);      cout<<" "<<p->data;      print_inorder(p->right); } void print_preorder(struct tree *p) {      if(p==NULL)return;      cout<<p->data;      print_preorder(p->left);      print_preorder(p->right); } void print_postorder(struct tree *p) {      if(p==NULL)return;      print_postorder(p->left);      print_postorder(p->right);      cout<<p->data; } void main() {  clrscr();  cout<<"\nEnter Infix Expression\n";  cin>>exp;  n=strlen(exp);  tree *q;  q=(tree*)malloc(sizeof(tree));  Exp_tree(q,0,n-1);  cout<<"\nInorder.: ";  print_inorder(q);  cout<<"\nPreorder.: ";  print_preorder(q);  cout<<"\nPostorder.: ";  print_postorder(q);  find(q);  cout<<"\nFinal Solution.: "<<q->data2.x;  getch(); }