• Source 
    1. #include<stdio.h>
    2. #include<stdlib.h>
    3. typedef struct d
    4. {
    5.     int root;
    6.     struct d *left;
    7.     struct d *right;
    8. }TREE;
    9.  
    10. TREE *parent=NULL, *location=NULL;
    11. TREE *create(TREE *t, int num)
    12. {
    13.     if(t==NULL){
    14.         t = (TREE *) malloc(sizeof(TREE) );
    15.         t->root=num;
    16.         t->left=t->right=NULL;
    17.     }
    18.  
    19.     else if(num<t->root)
    20.         t->left=create(t->left,num);
    21.     else if(num>t->root)
    22.         t->right=create(t->right, num);
    23.     return t;
    24. }
    25.  
    26. void print(int height, TREE *t)
    27. {
    28.     int i=0;
    29.     if(NULL!=t){
    30.         print(height+1, t->right);
    31.         printf("\n ");
    32.  
    33.         for(i=0;i<height;i++)
    34.             printf(" ");
    35.  
    36.         printf(" %d ",t->root);
    37.         print(height+1, t->left);
    38.  
    39.     }
    40.  
    41. }
    42.  
    43. void search(int item,TREE *ptr)
    44. {
    45.      while( item!=ptr->root)
    46.      {
    47.             parent=ptr;
    48.             if(item<ptr->root)
    49.                               ptr=ptr->left;
    50.  
    51.             else
    52.                 ptr=ptr->right;
    53.  
    54.         location=ptr;      // ptr is changed
    55.  
    56.      }
    57. }
    58.  
    59. int sma(TREE *t)
    60. {
    61.  
    62.     if(t->root==NULL)
    63.         return 0;   
    64.     while(t->left!=NULL){
    65.         t=t->left;
    66.     }
    67.     //printf("do\n");
    68. return t->root;
    69. }
    70.  
    71. int main()
    72. {
    73.     TREE *tree=NULL, *x, *y;
    74.     int n;
    75.     while(1){
    76.  
    77.         printf("\ngive value :");
    78.         scanf("%d",&n);
    79.         if(n==999)
    80.             break;
    81.         tree=create(tree, n);   
    82.     }
    83.  
    84.     print(1, tree);     //  ******************      printing the tree
    85.     printf("\nGive value to find location & parent:");
    86.     scanf("%d",&n);
    87.     search(n,tree);    //    *****************      Parent
    88.  
    89.    if(location==NULL)
    90.             printf("It have no Parent\n");
    91.     else
    92.         printf("\nThe parent of node is %d given value %d\n",parent->root, location->root);   
    93.  
    94.  
    95. // ***************************************************       the part of successor
    96.  
    97.     x=location;
    98.  
    99.     y=parent;
    100.  
    101.     if(x==NULL)
    102.         x=tree;            // if the given number is root
    103.  
    104.  
    105.     if(x->right!=NULL){
    106.        int minimum=sma(x->right);
    107.        printf("The successor is %d of %d\n",minimum, x->root);
    108.     }
    109.     else{
    110.          while(y!=NULL && y->right!=NULL && (x->root== y->right->root) )
    111.         {
    112.            x=y;
    113.           search(y->root, tree);
    114.           y=parent;
    115.          }
    116.          printf("The successor is %d\n",y->root);
    117.     }                 
    118.  
    119.     free(tree);
    120.     getchar();
    121.     return 0;
    122. }