【算法集训】基础数据结构：六、栈和队列

做这几天的数据结构的题目的时候有很多函数需要填写，这里需要有一个大致的顺序，一般是先补全结构体，也就是创建队列 | 栈；
而后初始化，设置初值create（）函数，再然后C语言需要释放，补全释放函数也就是free；
这下可以根据题目要求进行操作了，一般情况下模拟操作自己是可以做出来的，但是像我第一次看到这个题目肯定是一脸懵逼，只有看了视频才知道。
数据结构我感觉就是孰能生巧的东西，不像算法变化很多，还是要多敲代码记住就可以了。

第一题面试题 03.04. 化栈为队

第一种：这里初始化顶部为0，所以要访问顶部的话需要-1再进行访问。

// 题目要求两个栈,这里用数组创建两个栈
typedef struct {int stackin[30000], topin;int stackout[30000], topout;
} MyQueue;/** Initialize your data structure here. */
//创建"队列",初始化
MyQueue* myQueueCreate() {MyQueue * obj = (MyQueue *)malloc(sizeof(MyQueue));obj->topin = 0;obj->topout = 0;return obj;
}/** 往队列中加入元素. */
void myQueuePush(MyQueue* obj, int x) {obj->stackin[obj->topin++] = x;
}/** 移除队列的头部 */
int myQueuePop(MyQueue* obj) {if(obj->topout == 0) {while(obj->topin) {obj->stackout[obj->topout++] = obj->stackin[--obj->topin];}}return obj->stackout[--obj->topout];
}/** 获取队列的头部(不删除). */
int myQueuePeek(MyQueue* obj) {if(obj->topout == 0) {while(obj->topin) {obj->stackout[obj->topout++] = obj->stackin[--obj->topin];}}return obj->stackout[obj->topout - 1];
}/** 判断队列是否为空. */
bool myQueueEmpty(MyQueue* obj) {return obj->topin + obj->topout == 0;
}
// 释放队列
void myQueueFree(MyQueue* obj) {free(obj);
}/*** Your MyQueue struct will be instantiated and called as such:* MyQueue* obj = myQueueCreate();* myQueuePush(obj, x);* int param_2 = myQueuePop(obj);* int param_3 = myQueuePeek(obj);* bool param_4 = myQueueEmpty(obj);* myQueueFree(obj);
*/

第二种：这里初始化顶部为1

typedef struct {int stackin[30000], topin;int stackout[30000], topout;
} MyQueue;/** Initialize your data structure here. */MyQueue* myQueueCreate() {MyQueue * obj = (MyQueue *)malloc(sizeof(MyQueue));obj->topin = -1;obj->topout = -1;return obj;
}/** Push element x to the back of queue. */
void myQueuePush(MyQueue* obj, int x) {obj->stackin[++obj->topin] = x;
}/** Removes the element from in front of queue and returns that element. */
int myQueuePop(MyQueue* obj) {if(obj->topout == -1) {while(obj->topin != -1) {obj->stackout[++obj->topout] = obj->stackin[obj->topin--];}}return obj->stackout[obj->topout--];
}/** Get the front element. */
int myQueuePeek(MyQueue* obj) {if(obj->topout == -1) {while(obj->topin != -1) {obj->stackout[++obj->topout] = obj->stackin[obj->topin--];}}return obj->stackout[obj->topout];
}/** Returns whether the queue is empty. */
bool myQueueEmpty(MyQueue* obj) {return obj->topin + obj->topout == -2;
}void myQueueFree(MyQueue* obj) {free(obj);
}/*** Your MyQueue struct will be instantiated and called as such:* MyQueue* obj = myQueueCreate();* myQueuePush(obj, x);* int param_2 = myQueuePop(obj);* int param_3 = myQueuePeek(obj);* bool param_4 = myQueueEmpty(obj);* myQueueFree(obj);
*/

第二题 LCR 125. 图书整理 II

这里删除图书那里，和上一题不一样，上一题保证没有空的，但这一题是有空的，这里需要进行一个判断，如果两个栈都为空则返回-1；

typedef struct {int stackin[10001], topin;int stackout[10001], topout;
} CQueue;CQueue* cQueueCreate() {CQueue * obj = (CQueue *)malloc(sizeof(CQueue));obj->topin = 0;obj->topout = 0;return obj;
}void cQueueAppendTail(CQueue* obj, int value) {obj->stackin[obj->topin++] = value;
}int cQueueDeleteHead(CQueue* obj) {if(obj->topout == 0) {while(obj->topin) {obj->stackout[obj->topout++] = obj->stackin[--obj->topin];}}if(obj->topout == 0) {return -1;}else {return obj->stackout[--obj->topout];}}void cQueueFree(CQueue* obj) {free(obj);
}/*** Your CQueue struct will be instantiated and called as such:* CQueue* obj = cQueueCreate();* cQueueAppendTail(obj, value);* int param_2 = cQueueDeleteHead(obj);* cQueueFree(obj);
*/

第三题 232. 用栈实现队列

typedef struct {int stackin[101], topin;int stackout[101], topout;
} MyQueue;MyQueue* myQueueCreate() {MyQueue * obj = (MyQueue *)malloc(sizeof(MyQueue));obj->topin = -1;obj->topout = -1;return obj;
}void myQueuePush(MyQueue* obj, int x) {obj->stackin[++obj->topin] = x;
}int myQueuePop(MyQueue* obj) {if(obj->topout == -1) {while(obj->topin != -1) {obj->stackout[++obj->topout] = obj->stackin[obj->topin--];}}return obj->stackout[obj->topout--];
}int myQueuePeek(MyQueue* obj) {if(obj->topout == -1) {while(obj->topin != -1) {obj->stackout[++obj->topout] = obj->stackin[obj->topin--];}}return obj->stackout[obj->topout];
}bool myQueueEmpty(MyQueue* obj) {return obj->topin + obj->topout == -2;
}void myQueueFree(MyQueue* obj) {free(obj);
}/*** Your MyQueue struct will be instantiated and called as such:* MyQueue* obj = myQueueCreate();* myQueuePush(obj, x);* int param_2 = myQueuePop(obj);* int param_3 = myQueuePeek(obj);* bool param_4 = myQueueEmpty(obj);* myQueueFree(obj);
*/

第四题 225. 用队列实现栈

// 创建队列
typedef struct {int head;int tail;int data[100001];
} MyQueue;void myQueueInit(MyQueue * obj) {obj->head = 0;obj->tail = -1;
}void myQueuePush(MyQueue * obj, int x) {obj->data[++obj->tail] = x;
}int myQueuePop(MyQueue * obj) {return obj->data[obj->head++];
}int myQueueTop(MyQueue * obj) {return obj->data[obj->head];
}int myQueueSize(MyQueue * obj) {return obj->tail - obj->head + 1;
}typedef struct {MyQueue q[2];int pushIdx;
} MyStack;MyStack* myStackCreate() {MyStack * obj = (MyStack *)malloc( sizeof(MyStack) );for(int i = 0; i < 2; i++) {myQueueInit( &obj->q[i]);}obj->pushIdx = 0;return obj;
}void myStackPush(MyStack* obj, int x) {MyQueue * q = &(obj->q[obj->pushIdx]);myQueuePush( q, x);
}int myStackPop(MyStack* obj) {MyQueue * pushq = &(obj->q[obj->pushIdx]);MyQueue * emptyq = &(obj->q[1 - obj->pushIdx]);while( myQueueSize(pushq) > 1 ) {myQueuePush(emptyq, myQueuePop(pushq));}int ret = myQueuePop(pushq);obj->pushIdx = 1 - obj->pushIdx;return ret;
}int myStackTop(MyStack* obj) {MyQueue * pushq = &(obj->q[obj->pushIdx]);MyQueue * emptyq = &(obj->q[1 - obj->pushIdx]);while( myQueueSize(pushq) > 1 ) {myQueuePush(emptyq, myQueuePop(pushq));}int ret = myQueuePop(pushq); myQueuePush(emptyq, ret);obj->pushIdx = 1 - obj->pushIdx;return ret;
}bool myStackEmpty(MyStack* obj) {return myQueueSize(&(obj->q[obj->pushIdx]))  == 0;
}void myStackFree(MyStack* obj) {free(obj);
}/*** Your MyStack struct will be instantiated and called as such:* MyStack* obj = myStackCreate();* myStackPush(obj, x);* int param_2 = myStackPop(obj);* int param_3 = myStackTop(obj);* bool param_4 = myStackEmpty(obj);* myStackFree(obj);
*/