Pairs (binary-search-tree-approach).c

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

struct node {
	int data;
	struct node* left;
	struct node* right;
};

struct node* createNode(int data);
struct node* insert(struct node* node, int data);
void freeRoot(struct node* node);
void printRoot(struct node* node);
void solve(struct node* node, int k);
int search(struct node* node, int val);

int count;

int main() {
    struct node* root = NULL;
    int i, n, k;
    
    scanf("%d%d", &n, &k);
    
    int* nums = malloc(sizeof(int) * n);
    
    for (i = 0; i < n; i++) {
        scanf("%d", &nums[i]);
        root = insert(root, nums[i]);
    }
    
    for (i = 0; i < n; i++) {
        if (search(root, nums[i] + k)) {
            count++;
        }
    }
    
    printf("%d\n", count);
    
    free(nums);
    freeRoot(root);
}

struct node* createNode(int data) {
    struct node* temp = malloc(sizeof(struct node));
    temp->data = data;
    temp->left = NULL;
    temp->right = NULL;
    
    return temp;
}

struct node* insert(struct node* node, int data) {
    if (node == NULL) {
        return createNode(data);
    }
    if (data > node->data) {
        node->right = insert(node->right, data);
    } else {
        node->left = insert(node->left, data);
    }
    return node;
}

void freeRoot(struct node* node) {
    if (node != NULL) {
        freeRoot(node->left);
        freeRoot(node->right);
        free(node);
    }
}

// Print root by in order
void printRoot(struct node* node) {
    if (node != NULL) {
        printRoot(node->left);
        printf("%d ", node->data);
        printRoot(node->right);
    }
}

int search(struct node* node, int val) {
    if (node == NULL) {
        return 0;
    }
    if (node->data == val) {
        return 1;
    } else if (node->data < val) {
        return search(node->right, val);
    } else {
        return search(node->left, val);
    }
}