队列的优化中,重新实现的方式确实提高了顺序队列和链式队列的效率, 可是实现过程还是比较复杂 。
可是这也是没有办法的 , 直接复用链表虽然可以实现队列 ,但是效率却不够好呀!
是不是有即能复用之前的代码 , 又比较高效的队列实现算法呢?
算法框架:
特殊队列的创建:
typedef struct _tag_SQueue { LinkStack* inStack; LinkStack* outStack; } TSQueue; SQueue* SQueue_Create() // O(1) { TSQueue* ret = (TSQueue*)malloc(sizeof(TSQueue)); if( ret != NULL ) { ret->inStack = LinkStack_Create(); ret->outStack = LinkStack_Create(); //创建两个栈 //是否创建成功 if( (ret->inStack == NULL) || (ret->outStack == NULL) ) { LinkStack_Destroy(ret->inStack); LinkStack_Destroy(ret->outStack); free(ret); ret = NULL; } } return ret; }
入队列:
int SQueue_Append(SQueue* queue, void* item) // O(1) { TSQueue* sQueue = (TSQueue*)queue; if( sQueue != NULL ) { LinkStack_Push(sQueue->inStack, item); } }
出队列:
void* SQueue_Retrieve(SQueue* queue) // O(1) { TSQueue* sQueue = (TSQueue*)queue; void* ret = NULL; if( sQueue != NULL ) { if( LinkStack_Size(sQueue->outStack) == 0 ) { while( LinkStack_Size(sQueue->inStack) > 0 ) { LinkStack_Push(sQueue->outStack, LinkStack_Pop(sQueue->inStack)); } } ret = LinkStack_Pop(sQueue->outStack); } return ret; }
头元素:
void* SQueue_Header(SQueue* queue) // O(1) { TSQueue* sQueue = (TSQueue*)queue; void* ret = NULL; if( sQueue != NULL ) { if( LinkStack_Size(sQueue->outStack) == 0 ) { while( LinkStack_Size(sQueue->inStack) > 0 ) { LinkStack_Push(sQueue->outStack, LinkStack_Pop(sQueue->inStack)); } } ret = LinkStack_Top(sQueue->outStack); } return ret; }
队列的长度:
int SQueue_Length(SQueue* queue) // O(1) { TSQueue* sQueue = (TSQueue*)queue; int ret = -1; if( sQueue != NULL ) { ret = LinkStack_Size(sQueue->inStack) + LinkStack_Size(sQueue->outStack); } return ret; }
main函数:
#include <stdio.h> #include <stdlib.h> #include "SQueue.h" /* run this program using the console pauser or add your own getch, system("pause") or input loop */ int main(int argc, char *argv[]) { SQueue* queue = SQueue_Create(); int a[10] = {0}; int i = 0; for(i=0; i<10; i++) { a[i] = i + 1; SQueue_Append(queue, a + i); } printf("Header: %d\n", *(int*)SQueue_Header(queue)); printf("Length: %d\n", SQueue_Length(queue)); for(i=0; i<5; i++) { printf("Retrieve: %d\n", *(int*)SQueue_Retrieve(queue)); } printf("Header: %d\n", *(int*)SQueue_Header(queue)); printf("Length: %d\n", SQueue_Length(queue)); for(i=0; i<10; i++) { a[i] = i + 1; SQueue_Append(queue, a + i); } while( SQueue_Length(queue) > 0 ) { printf("Retrieve: %d\n", *(int*)SQueue_Retrieve(queue)); } SQueue_Destroy(queue); return 0; }
运行结果: