【LeetCode刷题日记】队列类题目常见题型

2023-05-16

文章目录

    • [225. 用队列实现栈](https://leetcode-cn.com/problems/implement-stack-using-queues/)
    • [剑指 Offer 09. 用两个栈实现队列](https://leetcode-cn.com/problems/yong-liang-ge-zhan-shi-xian-dui-lie-lcof/)
    • [239. 滑动窗口最大值](https://leetcode-cn.com/problems/sliding-window-maximum/)
    • [622. 设计循环队列](https://leetcode-cn.com/problems/design-circular-queue/)
    • [面试题 03.04. 化栈为队](https://leetcode-cn.com/problems/implement-queue-using-stacks-lcci/)
    • [641. 设计循环双端队列](https://leetcode-cn.com/problems/design-circular-deque/)

225. 用队列实现栈

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906124138700.png

[外链图片转存失败,源站可能有防盗链机制,建议将图片保存下来直接上传(img-j69eRzUl-1631408789824)(在这里插入图片描述

#define LEN 20
typedef struct queue {
    int *data;
    int head;
    int rear;
    int size;
} Queue;

typedef struct {
    Queue *queue1, *queue2;
} MyStack;

Queue *initQueue(int k) {
    Queue *obj = (Queue *)malloc(sizeof(Queue));
    obj->data = (int *)malloc(k * sizeof(int));
    obj->head = -1;
    obj->rear = -1;
    obj->size = k;
    return obj;
}

void enQueue(Queue *obj, int e) {
    if (obj->head == -1) {
        obj->head = 0;
    }
    obj->rear = (obj->rear + 1) % obj->size;
    obj->data[obj->rear] = e;
}

int deQueue(Queue *obj) {
    int a = obj->data[obj->head];
    if (obj->head == obj->rear) {
        obj->rear = -1;
        obj->head = -1;
        return a;
    }
    obj->head = (obj->head + 1) % obj->size;
    return a;
}

int isEmpty(Queue *obj) {
    return obj->head == -1;
}

MyStack *myStackCreate() {
    MyStack *obj = (MyStack *)malloc(sizeof(MyStack));
    obj->queue1 = initQueue(LEN);
    obj->queue2 = initQueue(LEN);
    return obj;
}

void myStackPush(MyStack *obj, int x) {
    if (isEmpty(obj->queue1)) {
        enQueue(obj->queue2, x);
    } else {
        enQueue(obj->queue1, x);
    }
}

int myStackPop(MyStack *obj) {
    if (isEmpty(obj->queue1)) {
        while (obj->queue2->head != obj->queue2->rear) {
            enQueue(obj->queue1, deQueue(obj->queue2));
        }
        return deQueue(obj->queue2);
    }
    while (obj->queue1->head != obj->queue1->rear) {
        enQueue(obj->queue2, deQueue(obj->queue1));
    }
    return deQueue(obj->queue1);
}

int myStackTop(MyStack *obj) {
    if (isEmpty(obj->queue1)) {
        return obj->queue2->data[obj->queue2->rear];
    }
    return obj->queue1->data[obj->queue1->rear];
}

bool myStackEmpty(MyStack *obj) {
    if (obj->queue1->head == -1 && obj->queue2->head == -1) {
        return true;
    }
    return false;
}

void myStackFree(MyStack *obj) {
    free(obj->queue1->data);
    obj->queue1->data = NULL;
    free(obj->queue1);
    obj->queue1 = NULL;
    free(obj->queue2->data);
    obj->queue2->data = NULL;
    free(obj->queue2);
    obj->queue2 = NULL;
    free(obj);
    obj = NULL;
}

-------------------------------------------------------------------------
class MyStack {
public:
    queue<int> queue1;
    queue<int> queue2;

    /** Initialize your data structure here. */
    MyStack() {

    }

    /** Push element x onto stack. */
    void push(int x) {
        queue2.push(x);
        while (!queue1.empty()) {
            queue2.push(queue1.front());
            queue1.pop();
        }
        swap(queue1, queue2);
    }
    
    /** Removes the element on top of the stack and returns that element. */
    int pop() {
        int r = queue1.front();
        queue1.pop();
        return r;
    }
    
    /** Get the top element. */
    int top() {
        int r = queue1.front();
        return r;
    }
    
    /** Returns whether the stack is empty. */
    bool empty() {
        return queue1.empty();
    }
};

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906124337842.png

typedef struct tagListNode {
    struct tagListNode* next;
    int val;
} ListNode;

typedef struct {
    ListNode* top;
} MyStack;

MyStack* myStackCreate() {
    MyStack* stk = calloc(1, sizeof(MyStack));
    return stk;
}

void myStackPush(MyStack* obj, int x) {
    ListNode* node = malloc(sizeof(ListNode));
    node->val = x;
    node->next = obj->top;
    obj->top = node;
}

int myStackPop(MyStack* obj) {
    ListNode* node = obj->top;
    int val = node->val;
    obj->top = node->next;
    free(node);

    return val;
}

int myStackTop(MyStack* obj) {
    return obj->top->val;
}

bool myStackEmpty(MyStack* obj) {
    return (obj->top == NULL);
}

void myStackFree(MyStack* obj) {
    while (obj->top != NULL) {
        ListNode* node = obj->top;
        obj->top = obj->top->next;
        free(node);
    }
    free(obj);
}

------------------------------------------------------------------------
class MyStack {
public:
    queue<int> q;

    /** Initialize your data structure here. */
    MyStack() {

    }

    /** Push element x onto stack. */
    void push(int x) {
        int n = q.size();
        q.push(x);
        for (int i = 0; i < n; i++) {
            q.push(q.front());
            q.pop();
        }
    }
    
    /** Removes the element on top of the stack and returns that element. */
    int pop() {
        int r = q.front();
        q.pop();
        return r;
    }
    
    /** Get the top element. */
    int top() {
        int r = q.front();
        return r;
    }
    
    /** Returns whether the stack is empty. */
    bool empty() {
        return q.empty();
    }
};

剑指 Offer 09. 用两个栈实现队列

在这里插入图片描述
在这里插入图片描述

class CQueue {
    stack<int> stack1,stack2;
public:
    CQueue() {
        while (!stack1.empty()) {
            stack1.pop();
        }
        while (!stack2.empty()) {
            stack2.pop();
        }
    }
    
    void appendTail(int value) {
        stack1.push(value);
    }
    
    int deleteHead() {
        // 如果第二个栈为空
        if (stack2.empty()) {
            while (!stack1.empty()) {
                stack2.push(stack1.top());
                stack1.pop();
            }
        } 
        if (stack2.empty()) {
            return -1;
        } else {
            int deleteItem = stack2.top();
            stack2.pop();
            return deleteItem;
        }
    }
};

239. 滑动窗口最大值

在这里插入图片描述
在这里插入图片描述

void swap(int** a, int** b) {
    int* tmp = *a;
    *a = *b, *b = tmp;
}

int cmp(int* a, int* b) {
    return a[0] == b[0] ? a[1] - b[1] : a[0] - b[0];
}

struct Heap {
    int** heap;
    int size;
    int capacity;
};

void init(struct Heap* obj, int capacity) {
    obj->size = 0;
    obj->heap = NULL;
    obj->capacity = capacity;
    obj->heap = malloc(sizeof(int*) * (obj->capacity + 1));
    for (int i = 1; i <= obj->capacity; i++) {
        obj->heap[i] = malloc(sizeof(int) * 2);
    }
}

void setFree(struct Heap* obj) {
    for (int i = 1; i <= obj->capacity; i++) {
        free(obj->heap[i]);
    }
    free(obj->heap);
    free(obj);
}

void push(struct Heap* obj, int num0, int num1) {
    int sub1 = ++(obj->size), sub2 = sub1 >> 1;
    (obj->heap[sub1])[0] = num0, (obj->heap[sub1])[1] = num1;
    while (sub2 > 0 && cmp(obj->heap[sub2], obj->heap[sub1]) < 0) {
        swap(&(obj->heap[sub1]), &(obj->heap[sub2]));
        sub1 = sub2, sub2 = sub1 >> 1;
    }
}

void pop(struct Heap* obj) {
    int sub = 1;
    swap(&(obj->heap[sub]), &(obj->heap[(obj->size)--]));
    while (sub <= obj->size) {
        int sub1 = sub << 1, sub2 = sub << 1 | 1;
        int maxSub = sub;
        if (sub1 <= obj->size && cmp(obj->heap[maxSub], obj->heap[sub1]) < 0) {
            maxSub = sub1;
        }
        if (sub2 <= obj->size && cmp(obj->heap[maxSub], obj->heap[sub2]) < 0) {
            maxSub = sub2;
        }
        if (sub == maxSub) {
            break;
        }
        swap(&(obj->heap[sub]), &(obj->heap[maxSub]));
        sub = maxSub;
    }
}

int* top(struct Heap* obj) {
    return obj->heap[1];
}

int* maxSlidingWindow(int* nums, int numsSize, int k, int* returnSize) {
    struct Heap* q = malloc(sizeof(struct Heap));
    init(q, numsSize);
    for (int i = 0; i < k; i++) {
        push(q, nums[i], i);
    }
    int* ans = malloc(sizeof(int) * (numsSize - k + 1));
    *returnSize = 0;
    ans[(*returnSize)++] = top(q)[0];

    for (int i = k; i < numsSize; ++i) {
        push(q, nums[i], i);
        while (top(q)[1] <= i - k) {
            pop(q);
        }
        ans[(*returnSize)++] = top(q)[0];
    }
    setFree(q);
    return ans;
}

------------------------------------------------------------------------
class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        int n = nums.size();
        priority_queue<pair<int, int>> q;
        for (int i = 0; i < k; ++i) {
            q.emplace(nums[i], i);
        }
        vector<int> ans = {q.top().first};
        for (int i = k; i < n; ++i) {
            q.emplace(nums[i], i);
            while (q.top().second <= i - k) {
                q.pop();
            }
            ans.push_back(q.top().first);
        }
        return ans;
    }
};

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906132327420.png

int* maxSlidingWindow(int* nums, int numsSize, int k, int* returnSize) {
    int q[numsSize];
    int left = 0, right = 0;
    for (int i = 0; i < k; ++i) {
        while (left < right && nums[i] >= nums[q[right - 1]]) {
            right--;
        }
        q[right++] = i;
    }
    *returnSize = 0;
    int* ans = malloc(sizeof(int) * (numsSize - k + 1));
    ans[(*returnSize)++] = nums[q[left]];
    for (int i = k; i < numsSize; ++i) {
        while (left < right && nums[i] >= nums[q[right - 1]]) {
            right--;
        }
        q[right++] = i;
        while (q[left] <= i - k) {
            left++;
        }
        ans[(*returnSize)++] = nums[q[left]];
    }
    return ans;
}

-------------------------------------------------------------------------
class Solution {
public:
    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
        int n = nums.size();
        deque<int> q;
        for (int i = 0; i < k; ++i) {
            while (!q.empty() && nums[i] >= nums[q.back()]) {
                q.pop_back();
            }
            q.push_back(i);
        }

        vector<int> ans = {nums[q.front()]};
        for (int i = k; i < n; ++i) {
            while (!q.empty() && nums[i] >= nums[q.back()]) {
                q.pop_back();
            }
            q.push_back(i);
            while (q.front() <= i - k) {
                q.pop_front();
            }
            ans.push_back(nums[q.front()]);
        }
        return ans;
    }
};

622. 设计循环队列

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906132746631.png

在这里插入图片描述
https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906132844093.png
https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906132911406.png
在这里插入图片描述

面试题 03.04. 化栈为队

在这里插入图片描述

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906133302016.png

typedef struct {
    int* stk;
    int stkSize;
    int stkCapacity;
} Stack;

Stack* stackCreate(int cpacity) {
    Stack* ret = malloc(sizeof(Stack));
    ret->stk = malloc(sizeof(int) * cpacity);
    ret->stkSize = 0;
    ret->stkCapacity = cpacity;
    return ret;
}

void stackPush(Stack* obj, int x) {
    obj->stk[obj->stkSize++] = x;
}

void stackPop(Stack* obj) {
    obj->stkSize--;
}

int stackTop(Stack* obj) {
    return obj->stk[obj->stkSize - 1];
}

bool stackEmpty(Stack* obj) {
    return obj->stkSize == 0;
}

void stackFree(Stack* obj) {
    free(obj->stk);
}

typedef struct {
    Stack* inStack;
    Stack* outStack;
} MyQueue;

MyQueue* myQueueCreate() {
    MyQueue* ret = malloc(sizeof(MyQueue));
    ret->inStack = stackCreate(100);
    ret->outStack = stackCreate(100);
    return ret;
}

void in2out(MyQueue* obj) {
    while (!stackEmpty(obj->inStack)) {
        stackPush(obj->outStack, stackTop(obj->inStack));
        stackPop(obj->inStack);
    }
}

void myQueuePush(MyQueue* obj, int x) {
    stackPush(obj->inStack, x);
}

int myQueuePop(MyQueue* obj) {
    if (stackEmpty(obj->outStack)) {
        in2out(obj);
    }
    int x = stackTop(obj->outStack);
    stackPop(obj->outStack);
    return x;
}

int myQueuePeek(MyQueue* obj) {
    if (stackEmpty(obj->outStack)) {
        in2out(obj);
    }
    return stackTop(obj->outStack);
}

bool myQueueEmpty(MyQueue* obj) {
    return stackEmpty(obj->inStack) && stackEmpty(obj->outStack);
}

void myQueueFree(MyQueue* obj) {
    stackFree(obj->inStack);
    stackFree(obj->outStack);
}

---------------------------------------------------------------------------
class MyQueue {
private:
    stack<int> inStack, outStack;

    void in2out() {
        while (!inStack.empty()) {
            outStack.push(inStack.top());
            inStack.pop();
        }
    }

public:
    MyQueue() {}

    void push(int x) {
        inStack.push(x);
    }

    int pop() {
        if (outStack.empty()) {
            in2out();
        }
        int x = outStack.top();
        outStack.pop();
        return x;
    }

    int peek() {
        if (outStack.empty()) {
            in2out();
        }
        return outStack.top();
    }

    bool empty() {
        return inStack.empty() && outStack.empty();
    }
};

641. 设计循环双端队列

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906133456065.png

https://raw.githubusercontent.com/xkyvvv/blogpic/main/pic1/image-20210906133533051.png

#include <iostream>
#include <vector>

using namespace std;

class MyCircularDeque {

private:
    vector<int> arr;
    int front;
    int rear;
    int capacity;

public:
    /** Initialize your data structure here. Set the size of the deque to be k. */
    MyCircularDeque(int k) {
        capacity = k + 1;
        arr.assign(capacity, 0);

        front = 0;
        rear = 0;
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    bool insertFront(int value) {
        if (isFull()) {
            return false;
        }
        front = (front - 1 + capacity) % capacity;
        arr[front] = value;
        return true;
    }

    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    bool insertLast(int value) {
        if (isFull()) {
            return false;
        }
        arr[rear] = value;
        rear = (rear + 1) % capacity;
        return true;
    }

    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    bool deleteFront() {
        if (isEmpty()) {
            return false;
        }
        // front 被设计在数组的开头,所以是 +1
        front = (front + 1) % capacity;
        return true;
    }

    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    bool deleteLast() {
        if (isEmpty()) {
            return false;
        }
        // rear 被设计在数组的末尾,所以是 -1
        rear = (rear - 1 + capacity) % capacity;
        return true;
    }

    /** Get the front item from the deque. */
    int getFront() {
        if (isEmpty()) {
            return -1;
        }
        return arr[front];
    }

    /** Get the last item from the deque. */
    int getRear() {
        if (isEmpty()) {
            return -1;
        }
        // 当 rear 为 0 时防止数组越界
        return arr[(rear - 1 + capacity) % capacity];
    }

    /** Checks whether the circular deque is empty or not. */
    bool isEmpty() {
        return front == rear;
    }

    /** Checks whether the circular deque is full or not. */
    bool isFull() {
        // 注意:这个设计是非常经典的做法
        return (rear + 1) % capacity == front;
    }
};

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque* obj = new MyCircularDeque(k);
 * bool param_1 = obj->insertFront(value);
 * bool param_2 = obj->insertLast(value);
 * bool param_3 = obj->deleteFront();
 * bool param_4 = obj->deleteLast();
 * int param_5 = obj->getFront();
 * int param_6 = obj->getRear();
 * bool param_7 = obj->isEmpty();
 * bool param_8 = obj->isFull();
 */`
本文内容由网友自发贡献,版权归原作者所有,本站不承担相应法律责任。如您发现有涉嫌抄袭侵权的内容,请联系:hwhale#tublm.com(使用前将#替换为@)

【LeetCode刷题日记】队列类题目常见题型 的相关文章

随机推荐