# RECOVER-BINARY-SEARCH-TREE leetcode Solution - Correct, Optimal and Working

``````/*
*  Author: Arpit Bhayani
*  https://arpitbhayani.me
*/
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <deque>
#include <iostream>
#include <list>
#include <limits>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>

#define ll long long

#define MIN(a, b) a < b ? a : b
#define MAX(a, b) a > b ? a : b

using namespace std;

int readline(char *str) {
int i = 0;
char ch;
while((ch = getchar()) != '\n') {
str[i++] = ch;
}
str[i] = '\0';
return i;
}

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

struct node * new_node(int val) {
struct node *t = (struct node *) malloc(sizeof(struct node));
t->val = val;
t->left = t->right = NULL;
return t;
}

void _recoverTree(struct node * root,
struct node ** first, struct node ** second,
struct node ** third, struct node ** prev) {

if(root == NULL) {
return;
}

_recoverTree(root->left, first, second, third, prev);

if( *prev != NULL && root->val < (*prev)->val) {
if(*first == NULL) {
*first = *prev;
*second = root;
}
else {
*third = root;
}
}

*prev = root;
_recoverTree(root->right, first, second, third, prev);

}

void recoverTree(struct node * root) {
struct node * first = NULL, * second = NULL, * third = NULL;
struct node * prev = NULL;

_recoverTree(root, &first, &second, &third, &prev);

if(first && third) {
int t = first->val;
first->val = third->val;
third->val = t;
}
else {
int t = first->val;
first->val = second->val;
second->val = t;
}
}

int main(int argc, char *argv[]) {
struct node * root = NULL;

root = new_node(5);
root->left = new_node(3);
root->right = new_node(1);
root->left->left = new_node(7);
root->left->right = new_node(4);
root->left->left->right = new_node(2);
root->right->right = new_node(8);

recoverTree(root);

return 0;
}
``````