update leetcode

Author: Liang Wang

leetcode/BeautifulArrangementII.cpp

@@ -0,0 +1,21 @@
+
+class Solution {
+public:
+ vector<int> constructArray(int n, int k) {
+ vector<int> res;
+ res.push_back(1);
+ bool to_right = true;
+ for (int delta = k; delta >= 1; --delta) {
+ if (to_right) {
+ res.push_back(res.back() + delta);
+ } else {
+ res.push_back(res.back() - delta);
+ }
+ to_right = !to_right;
+ }
+ for (int i = k + 2; i <= n; ++i) {
+ res.push_back(i);
+ }
+ return res;
+ }
+};

leetcode/JudgePoint24.cpp

@@ -0,0 +1,58 @@
+class Solution {
+private:
+ bool check(vector<double>& nums) {
+ if (nums.size() == 1) {
+ return abs(nums[0] - 24.0) < 1e-6;
+ }
+ int sz = nums.size();
+ bool ok = false;
+ for (int i = 0; i < sz; ++i) {
+ for (int j = i + 1; j < sz; ++j) {
+ vector<double> n_nums;
+ for (int k = 0; k < sz; ++k) {
+ if (k != i && k != j) {
+ n_nums.push_back(nums[k]);
+ }
+ }
+ // a + b
+ n_nums.push_back(nums[i] + nums[j]);
+ ok = ok || check(n_nums);
+ n_nums.pop_back();
+ // a - b
+ n_nums.push_back(nums[i] - nums[j]);
+ ok = ok || check(n_nums);
+ n_nums.pop_back();
+ // b - a
+ n_nums.push_back(nums[j] - nums[i]);
+ ok = ok || check(n_nums);
+ n_nums.pop_back();
+ // a * b
+ n_nums.push_back(nums[i] * nums[j]);
+ ok = ok || check(n_nums);
+ n_nums.pop_back();
+ // a / b
+ if (abs(nums[j]) > 1e-6) {
+ n_nums.push_back(nums[i] / nums[j]);
+ ok = ok || check(n_nums);
+ n_nums.pop_back();
+ }
+ // b / a
+ if (abs(nums[i]) > 1e-6) {
+ n_nums.push_back(nums[j] / nums[i]);
+ ok = ok || check(n_nums);
+ n_nums.pop_back();
+ }
+ if (ok) return true;
+ }
+ }
+ return false;
+ }
+public:
+ bool judgePoint24(vector<int>& nums) {
+ vector<double> d_nums;
+ for (auto& n : nums) {
+ d_nums.push_back(1.0 * n);
+ }
+ return this->check(d_nums);
+ }
+};

leetcode/MaximumSwap.cpp

@@ -0,0 +1,33 @@
+class Solution {
+private:
+ int compute(const vector<int>& digits) {
+ int res = 0;
+ for (auto& d : digits) {
+ res = res * 10 + d;
+ }
+ return res;
+ }
+public:
+ int maximumSwap(int num) {
+ vector<int> digits;
+ int res = num;
+ while (num > 0) {
+ digits.push_back(num % 10);
+ num = num / 10;
+ }
+ reverse(digits.begin(), digits.end());
+ int sz = digits.size();
+ for (int i = 0; i < sz; ++i) {
+ for (int j = i + 1; j < sz; ++j) {
+ if (digits[i] >= digits[j]) {
+ continue;
+ }
+ swap(digits[i], digits[j]);
+ int n_num = this->compute(digits);
+ res = max(res, n_num);
+ swap(digits[i], digits[j]);
+ }
+ }
+ return res;
+ }
+};

leetcode/SecondMinimumNodeInBinaryTree.cpp

@@ -0,0 +1,38 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ * int val;
+ * TreeNode *left;
+ * TreeNode *right;
+ * TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+private:
+ set<int> s;
+ void dfs(TreeNode* root) {
+ if (NULL == root) {
+ return;
+ } else {
+ this->s.insert(root->val);
+ dfs(root->left);
+ dfs(root->right);
+ }
+ }
+public:
+ int findSecondMinimumValue(TreeNode* root) {
+ if (root == NULL || root->left == NULL) {
+ return -1;
+ }
+ s.clear();
+ dfs(root);
+ if (s.size() < 2) {
+ return -1;
+ }
+ auto it = s.begin();
+ ++it;
+ return *it;
+ }
+};

leetcode/TrimBinarySearchTree.cpp

@@ -0,0 +1,28 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ * int val;
+ * TreeNode *left;
+ * TreeNode *right;
+ * TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+ TreeNode* trimBST(TreeNode* root, int low, int high) {
+ if (root == NULL) {
+ return NULL;
+ }
+ if (root->val < low) {
+ return trimBST(root->right, low, high);
+ } else if (root->val > high) {
+ return trimBST(root->left, low, high);
+ } else {
+ root->left = trimBST(root->left, low, high);
+ root->right = trimBST(root->right, low, high);
+ return root;
+ }
+ }
+};