春节刷题day19：LeetCode

剑指 Offer 13. 机器人的运动范围

剑指 Offer 33. 二叉搜索树的后序遍历序列

剑指 Offer 59 - II. 队列的最大值

剑指 Offer 31. 栈的压入、弹出序列

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1、剑指 Offer 13. 机器人的运动范围

class Solution {
    
    
public:
    int ans;
    bool vis[105][105];
    int dir[4][2] = {
    
    {
    
    0, -1}, {
    
    0, 1}, {
    
    -1, 0}, {
    
    1, 0}};
    int slove(int x, int y){
    
    
        int ret = 0;
        while(x){
    
    
            ret += x % 10; x /= 10;
        }
        while(y){
    
    
            ret += y % 10; y /= 10;
        }
        return ret;
    }
    bool check(pair<int, int> now, int m, int n, int k){
    
    
        if(now.first >= m || now.first < 0) return false;
        if(now.second >= n || now.second < 0) return false;
        if(slove(now.first, now.second) > k) return false;
        if(vis[now.first][now.second]) return false;
        return true;
    }
    int movingCount(int m, int n, int k) {
    
    
        pair<int, int>now;
        queue< pair<int, int> > que;
        que.push(make_pair(0, 0));
        vis[0][0] = true;
        while(!que.empty()){
    
    
            now = que.front(); que.pop();
            int ret = 0;
            ans++;
            for(int i = 0; i < 4; i++){
    
    
                pair<int, int> nxt;
                nxt.first = now.first + dir[i][0];
                nxt.second = now.second + dir[i][1];
                if(check(nxt, m, n, k)){
    
    
                    vis[nxt.first][nxt.second] = true;
                    que.push(nxt);
                }
            }
        }
        return ans;
    }
};

2、剑指 Offer 33. 二叉搜索树的后序遍历序列

class Solution {
    
    
public:
    bool slove(vector<int>& postorder, int x, int y){
    
    
        if(x >= y) return true;
        int a = x;
        while(postorder[a] < postorder[y]) a++;
        int b = a;
        while(postorder[a] > postorder[y]) a++;
        return a == y && slove(postorder, x, b - 1) && slove(postorder, b, y - 1);
    }
    bool verifyPostorder(vector<int>& postorder) {
    
    
        return slove(postorder, 0, postorder.size() - 1);
    }
};

3、剑指 Offer 59 - II. 队列的最大值

class MaxQueue {
    
    
public:
    queue<int> que1;
    deque<int> que2;
    MaxQueue() {
    
    
        ;
    }
    
    int max_value() {
    
    
        if(que2.size() == 0) return -1;
        return que2.front();
    }
    
    void push_back(int value) {
    
    
        que1.push(value);
        while(!que2.empty() && que2.back() < value){
    
    
            que2.pop_back();
        }
        que2.push_back(value);
    }
    
    int pop_front() {
    
    
        if(que1.size() == 0) return -1;
        int ans = que1.front();
        que1.pop();
        if(ans == que2.front()) que2.pop_front();
        return ans;
    }
};

/**
 * Your MaxQueue object will be instantiated and called as such:
 * MaxQueue* obj = new MaxQueue();
 * int param_1 = obj->max_value();
 * obj->push_back(value);
 * int param_3 = obj->pop_front();
 */

4、剑指 Offer 31. 栈的压入、弹出序列

class Solution {
    
    
public:
    bool validateStackSequences(vector<int>& pushed, vector<int>& popped) {
    
    
        stack<int> st;
        int n = popped.size();
        int j = 0;
        for (int i = 0; i < pushed.size(); ++i){
    
    
            st.push(pushed[i]);
            while(!st.empty() && j < n && st.top() == popped[j]){
    
    
                st.pop();
                ++j;
            }
        }
        return st.empty();
    }
};

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2021/2/27。