http://www.geeksforgeeks.org/check-if-a-given-binary-tree-is-sumtree/
1 #include <iostream> 2 #include <vector> 3 #include <algorithm> 4 #include <queue> 5 #include <stack> 6 #include <string> 7 #include <fstream> 8 using namespace std; 9 10 struct node { 11 int data; 12 struct node *left, *right; 13 node() : data(0), left(NULL), right(NULL) { } 14 node(int d) : data(d), left(NULL), right(NULL) { } 15 }; 16 17 bool isleaf(node *root) { 18 return !root->left && !root->right; 19 } 20 21 bool issumtree(node *root) { 22 if (!root || isleaf(root)) return true; 23 int l = 0; 24 int r = 0; 25 if (root->left == NULL) l = 0; 26 else if (isleaf(root->left)) l = root->left->data; 27 else l = 2 * root->left->data; 28 if (root->right == NULL) r = 0; 29 else if (isleaf(root->right)) r = root->right->data; 30 else r = 2 * root->right->data; 31 return root->data == l + r && issumtree(root->left) && issumtree(root->right); 32 } 33 34 int main() { 35 node *root = new node(26); 36 root->left = new node(10); 37 root->right = new node(3); 38 root->left->left = new node(4); 39 root->left->right = new node(6); 40 root->right->right = new node(3); 41 if (issumtree(root)) cout << "yes" << endl; 42 else cout << "NO" << endl; 43 return 0; 44 }