leetcode 563

Posted 2021-01-24 热之雪

563. Binary Tree Tilt

Input: 
         1
       /         2     3
Output: 1
Explanation: 
Tilt of node 2 : 0
Tilt of node 3 : 0
Tilt of node 1 : |2-3| = 1
Tilt of binary tree : 0 + 0 + 1 = 1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    int findTilt(TreeNode* root) {
        if(root == NULL) return 0;
        
        int res = 0;
        
        postorder(root, res);
        
        return res;
    }
private:
    int postorder(TreeNode* root, int& res){
        if(root == NULL) return 0;
        
        int leftsum= postorder(root->left,res);
        
        int rightsum = postorder(root->right,res);
        
        res += abs(leftsum - rightsum);
        
        return leftsum + rightsum + root->val;
        
    }
};  

 

566. Reshape the Matrix

class Solution {
public:
    vector<vector<int>> matrixReshape(vector<vector<int>>& nums, int r, int c) {
        int m = nums.size(), n = nums[0].size(), o = m * n;
        if (r * c != o) return nums;
        vector<vector<int>> res(r, vector<int>(c, 0));
        for (int i = 0; i < o; i++) res[i / c][i % c] = nums[i / n][i % n];
        return res;
    }
};

 

 

572. Subtree of Another Tree

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    vector<TreeNode*> nodes;

public:
    bool isSubtree(TreeNode* s, TreeNode* t) {
        if (!s && !t) return true;
        if (!s || !t) return false;

        getDepth(s, getDepth(t, -1));

        for (TreeNode* n: nodes)
            if (identical(n, t))
                return true;

        return false;
    }

    int getDepth(TreeNode* r, int d) {
        if (!r)
            return -1;

        int depth = max(getDepth(r->left, d), getDepth(r->right, d)) + 1;

        // Check if depth equals required value
        // Require depth is -1 for tree t (only return the depth, no push)
        if (depth == d)  //递归回去得时候，从树下开始记达到深度位d时记下
            nodes.push_back(r);

        return depth;
    }

    bool identical(TreeNode* a, TreeNode* b) {
        if (!a && !b) return true;
        if (!a || !b || a->val != b->val) return false;

        return identical(a->left, b->left) && identical(a->right, b->right);
    }
};

 

 

581. Shortest Unsorted Continuous Subarray

Input: [2, 6, 4, 8, 10, 9, 15]
Output: 5
Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order.

class Solution {
    public int findUnsortedSubarray(int[] A) {
    int n = A.length, beg = -1, end = -2, min = A[n-1], max = A[0];
    for (int i=1;i<n;i++) {
      max = Math.max(max, A[i]);
      min = Math.min(min, A[n-1-i]);
      if (A[i] < max) end = i;
      if (A[n-1-i] > min) beg = n-1-i; 
    }
    return end - beg + 1;
}
}