738.单调递增的数字

链接地址

class Solution {
public:int monotoneIncreasingDigits(int n) {string str = to_string(n);int flag = str.size();for (int i = str.size() - 1; i > 0; i--) {if (str[i] < str[i - 1]) {str[i - 1] -= 1;flag = i;}}for (int j = flag; j < str.size(); j++) {str[j] = '9';}return stoi(str);}
};

968.监控二叉树

链接地址

/*** 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:int Tranversal(TreeNode* root, int& result) {if (root == nullptr) return 2;int left = Tranversal(root->left, result);int right = Tranversal(root->right, result);if (left == 2 && right == 2) {return 0;}//情况1：if (left == 0 || right == 0) {result++;return 1;}if (left == 1 || right == 1) {return 2;} return -1;}
public:int minCameraCover(TreeNode* root) {int result = 0;if (Tranversal(root, result) == 0) {result++;}return result;}
};

56. 合并区间

链接地址

class Solution {
public:vector<vector<int>> merge(vector<vector<int>>& intervals) {vector<vector<int>> result;if (intervals.size() == 0) return result;sort(intervals.begin(), intervals.end(), [](const vector<int>& a, const vector<int>& b){return a[0] < b[0];});result.push_back(intervals[0]);for (int i = 0; i < intervals.size(); i++) {if (result.back()[1] >= intervals[i][0]) {result.back()[1] = max(intervals[i][1], result.back()[1]); } else {result.push_back(intervals[i]);}}return result;}
};