This post focuses on the Binary search tree (BST) and the implementation of a Binary Search Tree program for Insertion, Deletion, and Traversal in C.
What is a Binary Search Tree (BST)?
It is one of the most used data structures where the nodes are placed together in a tree-like structure. Tree-like structure refers to the structure where there is a parent node and each parent is linked with its child nodes. But in BST a parent node cannot have more than two child nodes. The top node being the root node in the structure.
NOTE:
The child nodes on the left of its parent node are equal to its parent node.
The child nodes in the right of its parent node are greater than its parent node.
C Program for Binary Search Tree (BST)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 | #include < stdio.h > #include <malloc.h > struct node { int info; struct node * lchild; struct node * rchild; }*root; void find(int item, struct node **par, struct node **loc) { struct node *ptr, *ptrsave; if (root == NULL) { *loc = NULL; *par = NULL; return; } if (item == root->info) { *loc = root; *par = NULL; return; } if (item < root->info) ptr = root->lchild; else ptr = root->rchild; ptrsave = root; while (ptr != NULL) { if (item == ptr->info) {*loc = ptr; *par = ptrsave; return; } ptrsave = ptr; if (item < ptr->info) ptr = ptr->lchild; else ptr = ptr->rchild; } *loc = NULL; *par = ptrsave; } void insert(int item) { struct node *tmp, *parent, *location; find(item, &parent, &location); if (location != NULL) { printf("Item already present"); return; } tmp = (struct node *) malloc(sizeof(struct node)); tmp->info = item; tmp->lchild = NULL; tmp->rchild = NULL; if (parent == NULL) root = tmp; else if (item < parent->info) parent->lchild = tmp; else parent->rchild = tmp; } void case_a(struct node *par, struct node *loc) { if (par == NULL) root = NULL; else if (loc == par->lchild) par->lchild = NULL; else par->rchild = NULL; } void case_b(struct node *par, struct node *loc) { struct node * child; //intializing child if (loc->lchild != NULL) child = loc->lchild; else child = loc->rchild; if (par == NULL) root = child; else if (loc == par->lchild) par->lchild = child; else par->rchild = child; } void case_c(struct node *par, struct node *loc) { struct node *ptr, *ptrsave, *suc, *parsuc; ptrsave = loc; ptr = loc->rchild; while (ptr->lchild != NULL) { ptrsave = ptr; ptr = ptr->lchild; } suc = ptr; parsuc = ptrsave; if (suc->lchild == NULL && suc->rchild == NULL) case_a(parsuc, suc); else case_b(parsuc, suc); if (par == NULL) root = suc; else if (loc == par->lchild) par->lchild = suc; else par->rchild = suc; suc->lchild = loc->lchild; suc->rchild = loc->rchild; } int del(int item) { struct node *parent, *location; if (root == NULL) { printf("Tree empty"); return 0; } find(item, &parent, &location); if (location == NULL) { printf("Item not present in tree"); return 0; } if (location->lchild == NULL && location->rchild == NULL) case_a(parent, location); if (location->lchild != NULL && location->rchild == NULL) case_b(parent, location); if (location->lchild == NULL && location->rchild != NULL) case_b(parent, location); if (location->lchild != NULL && location->rchild != NULL) case_c(parent, location); free(location); } int preorder(struct node *ptr) { if (root == NULL) { printf("Tree is empty"); return 0; } if (ptr != NULL) { printf("%d ", ptr->info); preorder(ptr->lchild); preorder(ptr->rchild); } } void inorder(struct node *ptr) { if (root == NULL) { printf("Tree is empty"); return; } if (ptr != NULL) { inorder(ptr->lchild); printf("%d ", ptr->info); inorder(ptr->rchild); } } void postorder(struct node *ptr) { if (root == NULL) { printf("Tree is empty"); return; } if (ptr != NULL) { postorder(ptr->lchild); postorder(ptr->rchild); printf("%d ", ptr->info); } } void display(struct node *ptr, int level) { int i; if (ptr != NULL) { display(ptr->rchild, level + 1); printf("\n"); for (i = 0; i < level; i++) printf(" "); printf("%d", ptr->info); display(ptr->lchild, level + 1); } } main() { int choice, num; root = NULL; while (1) { printf("\n"); printf("1.Insert\n"); printf("2.Delete\n"); printf("3.Inorder Traversal\n"); printf("4.Preorder Traversal\n"); printf("5.Postorder Traversal\n"); printf("6.Display\n"); printf("7.Quit\n"); printf("Enter your choice : "); scanf("%d", &choice); switch (choice) { case 1: printf("Enter the number to be inserted : "); scanf("%d", &num); insert(num); break; case 2: printf("Enter the number to be deleted : "); scanf("%d", &num); del(num); break; case 3: inorder(root); break; case 4: preorder(root); break; case 5: postorder(root); break; case 6: display(root, 1); break; case 7: break; default: printf("Wrong choice\n"); } } } |
Output of Binary Search Tree Program in C: After execution following will be displayed in Screen.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 | 1.Insert 2.Delete 3.Inorder Traversal 4.Preorder Traversal 5.Postorder Traversal 6.Display 7.Quit Enter your choice : 1 Enter the number to be inserted : 250 1.Insert 2.Delete 3.Inorder Traversal 4.Preorder Traversal 5.Postorder Traversal 6.Display 7.Quit Enter your choice : 1 Enter the number to be inserted : 350 1.Insert 2.Delete 3.Inorder Traversal 4.Preorder Traversal 5.Postorder Traversal 6.Display 7.Quit Enter your choice : 4 Enter the number to be inserted : 250 250 350 1.Insert 2.Delete 3.Inorder Traversal 4.Preorder Traversal 5.Postorder Traversal 6.Display 7.Quit Enter your choice : 6 350 250 1.Insert 2.Delete 3.Inorder Traversal 4.Preorder Traversal 5.Postorder Traversal 6.Display 7.Quit Enter your choice : |