leetcode

Some Tree Problems

7 files changed, 168 insertions(+), 1 deletions(-)

diff --git a/ Problems/0110.cpp b/ Problems/0110.cpp

@@ -0,0 +1,23 @@

class Solution {

public:

bool isBalanced(TreeNode *root) {

if (!root) return true;

stack<TreeNode *> st;

st.push(root);

while (!st.empty()) {

TreeNode *root = st.top();

if (root == nullptr) {

st.pop(), root = st.top(), st.pop();

int left = root->left ? root->left->val : 0;

int right = root->right ? root->right->val : 0;

if (abs(right - left) > 1) return false;

root->val = max(left, right) + 1;

continue;

}

st.push(nullptr);

if (root->left) st.push(root->left);

if (root->right) st.push(root->right);

}

return true;

}

};

diff --git a/ Problems/0654.cpp b/ Problems/0654.cpp

@@ -0,0 +1,33 @@

class Solution {

struct record {

TreeNode **parent;

int start, end;

record(TreeNode **p, int s, int e) : parent(p), start(s), end(e) {}

};

public:

TreeNode *constructMaximumBinaryTree(vector<int> &nums) {

TreeNode *head, tmp;

stack<record> st;

head = new TreeNode(-1);

st.push({&head->right, 0, (int)nums.size()});

while (!st.empty()) {

auto [root, start, end] = st.top();

st.pop();

while (start < end) {

int index = -1;

for (int i = start, maxi = INT_MIN; i < end; i++)

if (nums[i] > maxi) {

maxi = nums[i];

index = i;

}

*root = new TreeNode(nums[index]);

st.push({&(*root)->left, start, index});

root = &(*root)->right;

start = index + 1;

}

}

return head->right;

}

};

diff --git a/ Problems/0671.cpp b/ Problems/0671.cpp

@@ -0,0 +1,21 @@

class Solution {

public:

int findSecondMinimumValue(TreeNode *root) {

if (!root) return -1;

int val = root->val;

long long res = LONG_MAX;

stack<TreeNode *> st;

st.push(root);

while (!st.empty()) {

TreeNode *root = st.top();

st.pop();

if (!root->left) continue;

int m = max(root->left->val, root->right->val);

if (m != val) res = min(res, (long long)m);

if (root->left->val == val) st.push(root->left);

if (root->right->val == val) st.push(root->right);

}

return res != LONG_MAX ? res : -1;

}

};

diff --git a/ Problems/1302.cpp b/ Problems/1302.cpp

@@ -0,0 +1,20 @@

class Solution {

public:

int deepestLeavesSum(TreeNode *root) {

int sum = 0;

queue<TreeNode *> q;

q.push(root);

while (!q.empty()) {

sum = 0;

for (int k = q.size(); k > 0; k--) {

TreeNode *root = q.front();

q.pop();

sum += root->val;

if (root->left) q.push(root->left);

if (root->right) q.push(root->right);

}

}

return sum;

}

};

diff --git a/ Problems/1315.cpp b/ Problems/1315.cpp

@@ -0,0 +1,31 @@

class Solution {

public:

int sumEvenGrandparent(TreeNode *root) {

stack<TreeNode *> st;

int sum = 0;

st.push(root);

while (!st.empty()) {

TreeNode *root = st.top();

st.pop();

if (root->left) {

st.push(root->left);

if (root->val % 2 == 0) {

if (root->left->left) sum += root->left->left->val;

if (root->left->right) sum += root->left->right->val;

}

}

if (root->right) {

st.push(root->right);

if (root->val % 2 == 0) {

if (root->right->left) sum += root->right->left->val;

if (root->right->right) sum += root->right->right->val;

}

}

}

return sum;

}

};

diff --git a/ Problems/2265.cpp b/ Problems/2265.cpp

@@ -0,0 +1,33 @@

class Solution {

public:

int averageOfSubtree(TreeNode *root) {

stack<TreeNode *> st;

unordered_map<TreeNode *, int> um;

int res = 0;

st.push(root);

while (!st.empty()) {

TreeNode *root = st.top();

if (root == nullptr) {

st.pop(), root = st.top(), st.pop();

int sum = root->val, count = 1;

if (root->left) {

sum += root->left->val;

count += um[root->left];

}

if (root->right) {

sum += root->right->val;

count += um[root->right];

}

if (root->val == sum / count) res++;

um[root] = count;

root->val = sum;

continue;

}

st.push(nullptr);

if (root->left) st.push(root->left);

if (root->right) st.push(root->right);

}

return res;

}

};

diff --git a/ README.md b/ README.md

@@ -48,6 +48,7 @@ if you have any questions. | 0107 | Medium | [Binary Tree Level Order Traversal II](Problems/0107.cpp) | | 0108 | Easy | [Convert Sorted Array to Binary Search Tree](Problems/0108.cpp) | | 0109 | Medium | [Convert Sorted List to Binary Search Tree](Problems/0109.cpp) |

| 0110 | Easy | [Balanced Binary Tree](Problems/0110.cpp) |

| 0111 | Easy | [Minimum Depth of Binary Tree](Problems/0111.cpp) | | 0112 | Easy | [Path Sum](Problems/0112.cpp) | | 0114 | Medium | [Flatten Binary Tree to Linked List](Problems/0114.cpp) |

@@ -94,6 +95,7 @@ if you have any questions. | 0283 | Easy | [Move Zeroes](Problems/0283.cpp) | | 0287 | Medium | [Find the Duplicate Number](Problems/0287.cpp) | | 0290 | Easy | [Word Pattern](Problems/0290.cpp) |

| 0295 | Hard | [Find Median from Data Stream](Problems/0295.cpp) |

| 0328 | Medium | [Odd Even Linked List](Problems/0328.cpp) | | 0338 | Easy | [Counting Bits](Problems/0338.cpp) | | 0344 | Easy | [Reverse String](Problems/0344.cpp) |

@@ -137,7 +139,9 @@ if you have any questions. | 0617 | Easy | [Merge Two Binary Trees](Problems/0617.cpp) | | 0637 | Easy | [Average of Levels in Binary Tree](Problems/0637.cpp) | | 0653 | Easy | [Two Sum IV - Input is a BST](Problems/0653.cpp) |

| 0654 | Medium | [Maximum Binary Tree](Problems/0654.cpp) |

| 0669 | Medium | [Trim a Binary Search Tree](Problems/0669.cpp) |

| 0671 | Easy | [Second Minimum Node In a Binary Tree](Problems/0671.cpp) |

| 0684 | Medium | [Redundant Connection](Problems/0684.cpp) | | 0700 | Easy | [Search in a Binary Search Tree](Problems/0700.cpp) | | 0701 | Medium | [Insert into a Binary Search Tree](Problems/0701.cpp) |

@@ -186,7 +190,9 @@ if you have any questions. | 1137 | Easy | [N-th Tribonacci Number](Problems/1137.cpp) | | 1209 | Medium | [Remove All Adjacent Duplicates in String II](Problems/1209.cpp) | | 1290 | Easy | [Convert Binary Number in a Linked List to Integer](Problems/1290.cpp) |

| 1302 | Medium | [Deepest Leaves Sum](Problems/1302.cpp) |

| 1305 | Medium | [All Elements in Two Binary Search Trees](Problems/1305.cpp) |

| 1315 | Medium | [Sum of Nodes with Even-Valued Grandparent](Problems/1315.cpp) |

| 1319 | Medium | [Number of Operations to Make Network Connected](Problems/1319.cpp) | | 1323 | Easy | [Maximum 69 Number](Problems/1323.cpp) | | 1337 | Easy | [The K Weakest Rows in a Matrix](Problems/1337.cpp) |

@@ -225,6 +231,7 @@ if you have any questions. | 2181 | Medium | [Merge Nodes in Between Zeros](Problems/2181.cpp) | | 2235 | Easy | [Add Two Integers](Problems/2235.cpp) | | 2236 | Easy | [Root Equals Sum of Children](Problems/2236.cpp) |

| 2265 | Medium | [Count Nodes Equal to Average of Subtree](Problems/2265.cpp) |

| 2279 | Medium | [Maximum Bags With Full Capacity of Rocks](Problems/2279.cpp) | | 2285 | Medium | [Maximum Total Importance of Roads](Problems/2285.cpp) | | 2326 | Medium | [Spiral Matrix IV](Problems/2326.cpp) |

@@ -234,7 +241,6 @@ if you have any questions. | 2465 | Easy | [Number of Distinct Averages](Problems/2465.cpp) | | 2466 | Medium | [Count Ways To Build Good Strings](Problems/2466.cpp) | | 2467 | Medium | [Most Profitable Path in a Tree](Problems/2467.cpp) |

| 2469 | Hard | [Find Median from Data Stream](Problems/0295.cpp) |

## DNF