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Copy path232_implement_queue_using_stacks.c
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232_implement_queue_using_stacks.c
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#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
typedef struct {
int *stack;
int *stack2;
int top;
int top2;
} Queue;
/* Create a queue */
void queueCreate(Queue *queue, int maxSize) {
queue->stack = (int *)malloc(sizeof(int)*maxSize);
queue->stack2 = (int *)malloc(sizeof(int)*maxSize);
queue->top = 0;
queue->top2 = 0;
}
/* Push element x to the back of queue */
void queuePush(Queue *queue, int element) {
queue->stack[queue->top++] = element;
}
/* Remove the element from front of queue */
void queuePop(Queue *queue) {
while(queue->top > 0)
*(queue->stack2+queue->top2++) = *(queue->stack+(--queue->top));
queue->top2--;
while(queue->top2 > 0)
*(queue->stack+queue->top++) = *(queue->stack2+(--queue->top2));
}
/* Get the front element */
int queuePeek(Queue *queue) {
int result = 0;
while(queue->top > 0)
*(queue->stack2+queue->top2++) = *(queue->stack+(--queue->top));
if(queue->top2 > 0)
result = *(queue->stack2+queue->top2-1);
while(queue->top2 > 0)
*(queue->stack+queue->top++) = *(queue->stack2+(--queue->top2));
return result;
}
/* Return whether the queue is empty */
int queueEmpty(Queue *queue) {
return queue->top==0;
}
/* Destroy the queue */
void queueDestroy(Queue *queue) {
free(queue->stack);
free(queue->stack2);
}
int main() {
Queue *queue = malloc(sizeof(Queue));
queueCreate(queue, 10);
queuePush(queue, 1);
queuePush(queue, 2);
queuePush(queue, 3);
queuePop(queue);
queuePop(queue);
assert(queuePeek(queue) == 3);
assert(queueEmpty(queue) == 0);
queueDestroy(queue);
return 0;
}