search-bst.c

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
	int data;
	struct Node *left, *right;
} Node;

Node* createNode(int data) {
	Node* n = (Node*)calloc(1, sizeof(Node));
	n->data = data;
	return n;
}

Node *insert(Node *root, int data) {
	if (!root) return createNode(data);

	if (data < root->data) root->left = insert(root->left, data);
	else root->right = insert(root->right, data);

	return root;
}

int search(Node *root, int s) {
	if (!root) return 0;

	if (root->data == s) return 1;

	if (s < root->data) return search(root->left, s);
	else return search(root->right, s);
}


int main() {
	int arr[] = {10, 16, 4, 25, 54, 12, 8, 3, 20, 32};
	int n = sizeof(arr) / sizeof(arr[0]);

	Node *root = NULL;

	for (int i = 0; i < n; i++) root = insert(root, arr[i]);

	int s; scanf("%d", &s);

	if (search(root, s)) {
		printf("HIT\n");
	} else {
		printf("MISS\n");
	}
}

sum-left-leaves.c

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
	int data;
	struct Node *left, *right;
} Node;

Node* createNode(int data) {
	Node* n = (Node*)calloc(1, sizeof(Node));
	n->data = data;
	return n;
}

int sum(Node *root) {
	if (!root) return 0;

	int s = 0;
	if (root->left) {
		if (!root->left->left && !root->left->right) s += root->left->data;
		else s += sum(root->left);
	}

	s += sum(root->right);

	return s;
}

int main() {
	Node *root = createNode(14);
	root->left = createNode(2);
	root->left->left = createNode(1);
	root->left->right = createNode(3);
	root->right = createNode(11);
	root->right->left = createNode(10);
	root->right->left->left = createNode(7);
	root->right->right = createNode(30);
	root->right->right->left = createNode(40);

	printf("Sum of left leaves: %d\n", sum(root));
	return 0;
}