queue.c

来自「在C语言环境下编写的利用队列计算向量的+」· C语言 代码 · 共 123 行

#include <stdio.h>
#include <stdlib.h>

#define FALSE 0
#define NULL 0

struct listst {
    int     dataitem;
    struct listst *  next;
} ;

typedef struct listst listelement;

void Menu (int *choice);
listelement * AddItem (listelement * list, int data);
listelement * RemoveItem (listelement * list);
void PrintQueue (listelement * list);
void ClearQueue (listelement * list);

int main () {
    listelement listmember, *list;
    int     data, choice;

    list = NULL;
    do {
	Menu (&choice);
	switch (choice) {
	    case 1: 
		printf ("Enter data item value to add  ");
		scanf ("%d", &data);
		list = AddItem (list, data);
		break;
	    case 2: 
		if (list == NULL)
		    printf ("Queue empty!\n");
		else
		    list = RemoveItem (list);
		break;
	    case 3: 
		PrintQueue (list);
		break;

	    case 'q': 
			printf("Byebye");
		break;

	    default: 
		printf ("Invalid menu choice - try again\n");
		break;
	}
    } while (choice != 'q');
    ClearQueue (list);
}				/* main */

void Menu (int *choice) {

    char    local;

    printf ("\nEnter\t1 to add item,\n\t2 to remove item\n\
\t3 to print queue\n\t4 to quit\n");
    do {
   	local = getchar ();
	if ( !( '0'< local &&  local < '5') && (local != '\n')) {
	    printf ("\nyou must enter an integer.\n");
	    printf ("Enter 1 to add, 2 to remove, 3 to print, q to quit\n");
	}
    } while (!('0'< local &&  local < '5'));
 

   *choice = (int) local - '0';
}

listelement * AddItem (listelement * list, int data) {

    listelement * lp = list;

    if (list != NULL) {
	while (list -> next != NULL)
	    list = list -> next;
	list -> next = (listelement  *) malloc (sizeof (listelement));
	list = list -> next;
	list -> next = NULL;
	list -> dataitem = data;
	return lp;
    }
    else {
	list = (listelement  *) malloc (sizeof (listelement));
	list -> next = NULL;
	list -> dataitem = data;
	return list;
    }
}

listelement * RemoveItem (listelement * list) {

    listelement * tempp;
    printf ("Element removed is %d\n", list -> dataitem);
    tempp = list -> next;
    free (list);
    return tempp;
}

void PrintQueue (listelement * list) {

    if (list == NULL)
	printf ("queue is empty!\n");
    else
	while (list != NULL) {
	    printf ("%d\t", list -> dataitem);
	    list = list -> next;
	}
    printf ("\n");
}

void ClearQueue (listelement * list) {

    while (list != NULL) {
	list = RemoveItem (list);
    }
}