Merge pull request #8 from miloserdow/bst

BST done

bst/bst.c

@@ -0,0 +1,174 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct Node {
+    int val;
+    struct Node* r;
+    struct Node* l;
+};
+
+typedef struct Node Node;
+
+Node* init(int x) {
+    Node* tmp = (Node*) malloc(sizeof(Node));
+    if (tmp == NULL) {
+        fprintf(stderr, "ERROR: malloc returned NULL\n");
+        exit(1);
+    }
+    tmp->val = x;
+    tmp->l = NULL;
+    tmp->r = NULL;
+    return tmp;
+}
+
+Node* insert(Node* root, int x) {
+    if (root == NULL) 
+        return init(x);
+    else if (root->val < x)
+        root->r = insert(root->r, x);
+    else if (root->val > x)
+        root->l = insert(root->l, x);
+    return root;
+}
+
+Node* min(Node* root) {
+    if (root == NULL)
+        return NULL;
+    while (root->l)
+        root = root->l;
+    return root;
+}
+
+int find(Node* root, int x) {
+    if (root->val == x) 
+        return 1;
+    if (root->val > x) {
+        if (root->l)
+            find(root->l, x);
+        else
+            return 0;
+    } else if (root->val < x) {
+        if (root->r)
+            find(root->r, x);
+        else
+            return 0;
+    }
+    return 0;
+}
+
+Node* erase(Node* root, int x) {
+    if (root == NULL)
+        return NULL;
+    if (root->val < x)
+        root->r = erase(root->r, x);
+    else if (root->val > x)
+        root->l = erase(root->l, x);
+    else {
+        if ((root->r) && (root->l)) {
+            Node* right_min = min(root->r);
+            root->val = right_min->val;
+            root->r = erase(root->r,right_min->val);
+            return root;
+        } else if (root->r) {
+            Node* cur = root->r;
+            free(root);
+            return cur;
+        } else if (root->l) {
+            Node* cur = root->l;
+            free(root);
+            return cur;
+        } else {
+            free(root);
+            return NULL;
+        }
+    }
+    return root;
+}
+
+void print(Node* root) {
+    if (root == NULL)
+        return;
+
+    printf("(%d ",root->val);
+    if (root->l)
+        print(root->l);
+    else
+        puts("null");
+    puts(" ");
+    if (root->r) {
+        print(root->r);
+        puts(")");
+    } 
+    else
+        puts(" null)");
+}
+
+void print_min(Node* root) {
+    if (root == NULL)
+        return;
+    print_min(root->l);
+    printf("%d\n", root->val);
+    print_min(root->r);
+}
+
+void print_max(Node* root) {
+    if (root == NULL)
+        return;
+    print_max(root->r);
+    printf("%d ", root->val);
+    print_max(root->l);
+}
+
+void clean_tree(Node* root) {
+    if (root == NULL)
+        return;
+    clean_tree(root->l);
+    clean_tree(root->r);
+    free(root);
+}
+
+int main() {
+    char c;
+    Node* root = NULL;
+    printf("Type the command (h for help)\n");
+    for (;;) {
+        do
+            c = getchar();
+        while (isspace(c));
+        int val;
+        switch (c) {
+        case 'a':
+            scanf("%d", &val);
+            root = insert(root, val);
+            break;
+        case 'r':
+            scanf("%d", &val);
+            root = erase(root, val);
+            break;
+        case 'p':
+            print(root);
+            break;
+        case 'x':
+            print_max(root);
+            break;
+        case 'm':
+            print_min(root);
+            break;
+        case 'q':
+            clean_tree(root);
+            return 0;
+        case 'h':
+            printf("a x - Add x to the tree\n");
+            printf("r x - Erase x\n");
+            printf("p   - Print the tree\n");
+            printf("x   - Print from min to max\n");
+            printf("m   - Print from max to min\n");
+            printf("q   - Quit\n");
+            break;
+        default:
+            printf("Invalid command. Use h for help\n");
+            break;
+        }
+    }
+    return 0;
+}