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#include <climits> | |
#include <stack> | |
typedef struct Holder { | |
Node* node; | |
int min; | |
int max; | |
Holder(Node* n, int min, int max): node(n), min(min), max(max) {} | |
} *Holder_p; | |
// Cracking the Coding Interview, Question 4.5 | |
// Implement a function to check if a binary tree is a binary search tree | |
// See https://gist.github.com/lowellbander/d8c2bfcaebd8cbcdf755 | |
// Also see https://gist.github.com/n2westman/371494b4da13b30b4ffa | |
// Tail Recursive (less elegant) implementation | |
// Using stack instead of queue for smaller space complexity while maintaining the same time complexity | |
bool isSearch(Node* root, int max = INT_MAX, int min = INT_MIN) { | |
stack<Holder_p> s; | |
s.push(new Holder(root, max, min)); | |
return isSearchHelper(*s); | |
} | |
bool isSearchHelper(*stack<Holder_p> s) { | |
if(s->empty()) return true; | |
Holder_p hold = s->pop(); | |
if (!hold->node) return isSearchHelper(s); | |
if (hold->node->value <= hold->min || hold->node->value > hold->max) return false; | |
s->push(new Holder(hold->node->left, hold->min, hold->node->value)); | |
s->push(new Holder(hold->node->right, hold->node->value, hold->max)); | |
delete hold; | |
return isSearchHelper(s); | |
} |
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