当 next() called.Not 返回 NULL 时，最后一个元素不断重复
Last element keeps repeating when next() is called.Not returning NULL
嘿，我正在尝试实现一个可以存储任何类型元素的通用列表迭代器。它还有其他文件来处理正整数类型和字符串类型。该文件编译正确。但是，当我在我的测试用例代码中调用 next() 函数时（ 特别是下面代码中的测试用例 2），它会打印出所有添加的元素，但是当它到达列表中的最后一个元素，当没有最后一个元素时，它会不断重复它应该 return NULL 的最后一个元素。
这是下一个函数：
void *next(IteratorG it){
Node *tempo;
if ((tempo = malloc(sizeof(Node))) == NULL) {
return 0;
}
if(it->curr->next==NULL)
{
return NULL;
}
tempo=it->curr;
it->curr=it->curr->next;
// move to next node in list
return tempo->value;
}
我正在使用 Linux 环境，错误是从结果中看出的。这是整个程序的代码：
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include "iteratorG.h"
typedef struct Node {
void *value; // value of thee list item
struct Node *prev;
// pointer previous node in list
struct Node *next;
// pointer to next node in list
// implemented struct here ..
} Node;
typedef struct IteratorGRep {
int numofit; // count of items in list
Node *head; // first node in list
Node *curr; // current node in list
Node *tail; // last node in list
ElmCompareFp cmpElm;
ElmNewFp newElm;
ElmFreeFp freeElm;
// implemented struct here ..
} IteratorGRep;
/*
//Your functions below ....
*/
IteratorG newIterator(ElmCompareFp cmpFp, ElmNewFp newFp, ElmFreeFp freeFp){
IteratorG newit;
if ((newit = malloc(sizeof (struct IteratorGRep)))==NULL)
{
printf("Error...! \n");
}
//assert (newit != NULL);
newit->numofit = 0;
newit->head = NULL;
newit->tail = NULL;
newit->curr = NULL;
newit->cmpElm=cmpFp;
newit->newElm=newFp;
newit->freeElm=freeFp;
return newit;
// implemented function here and changed return value
}
int add(IteratorG it, void *vp){
Node *temp;
if ((temp = malloc(sizeof(Node))) == NULL) {
return 0;
}
temp->value = it->newElm(vp);
temp->next=NULL;
if(it->curr==NULL)
{
//temp->next=it->curr;
it->curr=temp;
it->tail=it->head=it->curr;
}
temp->next=it->curr;
it->curr->prev=temp;
it->curr=temp;
it->head=it->curr;
//it->curr->prev=temp;
/*temp->next = it->curr;
it->curr = temp;
*/
// add node to list from front
return 1;
}
int hasNext(IteratorG it){
if(it->curr->next==NULL)
{
return 0;
}
// check if theres next element/node
return 1;
}
int hasPrevious(IteratorG it){
if(it->curr->prev!=NULL)
{
return 1;
}
// check if theres previous element/node
return 0;
}
void *next(IteratorG it){
Node *tempo;
if ((tempo = malloc(sizeof(Node))) == NULL) {
return 0;
}
if(it->curr->next==NULL)
{
return NULL;
}
tempo=it->curr;
it->curr=it->curr->next;
// implemented function here
return tempo->value;
}
void *previous(IteratorG it){
Node *tempor;
if ((tempor = malloc(sizeof(Node))) == NULL) {
return 0;
}
tempor=it->curr;
if(tempor->prev==NULL)
{
return NULL;
}
tempor=it->curr->prev;
it->curr=it->curr->prev;
//tempor=it->curr;
// move to next node in list
return tempor->value;
}
int del(IteratorG it){
if(it->curr->prev!=NULL)
{
Node *temp_curr=it->curr;
Node *temp_prev=it->curr->prev->prev;
temp_curr->prev=temp_prev;
temp_prev->next=temp_curr;
return 1;
}// delete previous node from list
else
return 0;
}
int set(IteratorG it, void *vp){
if(it->curr->prev!=NULL)
{
it->curr->prev->value=vp;
/*
Node *wep;
if ((wep = malloc(sizeof(Node))) == NULL) {
return 0;
}
wep->value=it->newElm(vp);
store_next=it->curr;
store_prev=it->curr->prev->prev;
store_next->prev=wep;
wep->next=store_next;
store_prev->next=wep;
wep->prev=store_prev;
*/
return 1;
}
// change previous node value with new
return 0;
}
IteratorG advance(IteratorG it, int n){
//To be implemented
//move forward by n times
return NULL;
}
void reverse(IteratorG it){
Node *curr = it->head;
Node *temp = NULL;
while(curr != NULL) {
temp = curr->next;
curr->next = curr->prev;
curr->prev = temp;
curr = temp;
}
temp = it->head;
it->head = it->tail;
it->tail = temp;// reverse elements of whole list
}
IteratorG find(IteratorG it, int (*fp) (void *vp) ){
// To be implemented
// Find elements of vp in list after current position and put in new list.return the list.
return NULL;
}
int distanceFromStart(IteratorG it){
Node *c=it->curr;
int count=0;
while(c->prev!=NULL)
{
c=c->prev;
count++;
}
return count;
// count number of elements from start of list to current position
}
int distanceToEnd(IteratorG it){
Node *cu=it->curr;
int count=0;
while(cu->next!=NULL)
{
cu=cu->next;
count++;
}
return count;
// count number of elements from end of list to current position
}
void reset(IteratorG it){
while(it->curr->prev!=NULL)
{
it->curr=it->curr->prev;
}
return;
// move current position to start of list
}
void freeIt(IteratorG it){
assert(it != NULL);
Node *curr, *prev;
curr = it->head;
while (curr != NULL) {
prev = curr;
curr = curr->next;
free(prev->value);
free(prev);
}
free(it); // free items
}
这是代码的头文件：
#ifndef LISTITERATORG_H
#define LISTITERATORG_H
#include <stdio.h>
typedef struct IteratorGRep *IteratorG;
typedef int (*ElmCompareFp)(void const *e1, void const *e2);
typedef void *(*ElmNewFp)(void const *e1);
typedef void (*ElmFreeFp)(void *e1);
IteratorG newIterator(ElmCompareFp cmpFp, ElmNewFp newFp, ElmFreeFp freeFp);
int add(IteratorG it, void *vp);
int hasNext(IteratorG it);
int hasPrevious(IteratorG it);
void *next(IteratorG it);
void *previous(IteratorG it);
int del(IteratorG it);
int set(IteratorG it, void *vp);
IteratorG advance(IteratorG it, int n);
void reverse(IteratorG it);
IteratorG find(IteratorG it, int (*fp) (void *vp) );
int distanceFromStart(IteratorG it);
int distanceToEnd(IteratorG it);
void reset(IteratorG it);
void freeIt(IteratorG it);
#endif
其中一个功能尚未实现，并在代码中指明。但我想这可能不是问题的根源。我发现这里没有正确使用 NULL。
编辑：
这是测试用例代码。只有上面程序中的测试用例代码没有错误：
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include "iteratorG.h"
#include "positiveIntType.h"
#include "stringType.h"
#define MAXARRAY 5
/* Helper Functions Below */
/* Returns 1 if marks >= 50, 0 otherwise */
int passMarks(void *marks){
return (*((int *) marks) >= 50);
/* Easy to understand below ..
int *ip = (int *) marks;
if(*ip >= 50) { return 1; }
else { return 0; }
*/
}
/* Returns 1 if str starts with "jo" */
int prefixJo(void *str){
return (strncmp("jo", (char *) str, 2) == 0) ;
}
/* A function to print a string from a void pointer */
void prnStr(void *vp){
assert(vp != NULL);
printf(" %s", (char *) vp );
}
/* A function to print an integer from a void pointer */
void prnInt(void *vp){
assert(vp != NULL);
printf(" %d", *((int *) vp) );
}
/* Prints previous element using the given function 'fp'
examples: prnPrev(it1, prnInt); prnPrev(it2, prnStr);
*/
void prnPrev(IteratorG it, void (*fp) (void *p) ){
void *prevP = previous(it);
assert(prevP != NULL);
printf("> Previous value is: ");
fp(prevP);
printf("\n");
}
/* Prints next element using the given function 'fp'
examples: prnNext(it1, prnInt); prnNext(it2, prnStr);
*/
void prnNext(IteratorG it, void (*fp) (void *p) ){
void *nextP = next(it);
assert(nextP != NULL);
printf("> Next value is: ");
fp(nextP);
printf("\n");
}
/* Prints elements of 'it' from current to last position
using the given function 'fp'. The current position
of 'it' will change to the end of the list.
examples: prnIt(it1, prnInt); prnIt(it2, prnStr);
*/
void prnIt(IteratorG it, void (*fp) (void *p) ){
int count = 0;
while(hasNext(it)){
void *nextP = next(it);
count++;
if(count > 1) { printf(", "); }
fp(nextP);
}
printf("\n");
}
/* Few Tests Below */
void test1(){
printf("\n--==== Test-01 ====------\n");
IteratorG it1 = newIterator(positiveIntCompare, positiveIntNew, positiveIntFree);
int a[MAXARRAY] = { 25, 78, 6, 82 , 11};
for(int i=0; i<MAXARRAY; i++){
int result = add(it1 , &a[i]);
printf("> Inserting %d: %s \n", a[i], (result==1 ? "Success" : "Failed") );
}
freeIt(it1);
printf("--==== End of Test-01 ====------\n");
}
void test2(){
printf("\n--==== Test-02 ====------\n");
IteratorG it1 = newIterator(positiveIntCompare, positiveIntNew, positiveIntFree);
int a[MAXARRAY] = { 72, 14, 62, 8, 93};
for(int i=0; i<MAXARRAY; i++){
int result = add(it1 , &a[i]);
printf("> Inserting %d: %s \n", a[i], (result==1 ? "Success" : "Failed") );
}
prnNext(it1, prnInt);
prnNext(it1, prnInt);
prnPrev(it1, prnInt);
int newVal1 = 55;
int result1 = set(it1, &newVal1);
printf("> Set value: %d ; return val: %d \n", newVal1, result1 );
prnPrev(it1, prnInt);
freeIt(it1);
printf("--==== End of Test-02 ====------\n");
}
int main(int argc, char *argv[])
{
test1();
test2();
return EXIT_SUCCESS;
}
在add函数中，第一次添加时，it->curr是null，它使temp->next指向它自己，而不是null，所以链表似乎没有尽头:
您的原始代码：
if(it->curr==NULL)
{
it->curr=temp; // the current element is the add element
it->tail=it->head=it->curr;
}
temp->next=it->curr; // for the first element, it->curr is already valued to temp : temp->next points to temp :(
add 函数可以是：
// add node to list from front
int add(IteratorG it, void *vp){
Node *temp;
if ((temp = malloc(sizeof(Node))) == NULL) {
return 0;
}
temp->value = it->newElm(vp);
temp->prev = null;
temp->next = it->curr;
if (it->curr != NULL)
it->curr->prev = temp;
it->curr = temp;
it->head = it->curr;
return 1;
}
此外，我知道这不是您要的，但是 丑陋的 内存泄漏 next 和 previous 函数...
嘿，我正在尝试实现一个可以存储任何类型元素的通用列表迭代器。它还有其他文件来处理正整数类型和字符串类型。该文件编译正确。但是，当我在我的测试用例代码中调用 next() 函数时（ 特别是下面代码中的测试用例 2），它会打印出所有添加的元素，但是当它到达列表中的最后一个元素，当没有最后一个元素时，它会不断重复它应该 return NULL 的最后一个元素。
这是下一个函数：
void *next(IteratorG it){
Node *tempo;
if ((tempo = malloc(sizeof(Node))) == NULL) {
return 0;
}
if(it->curr->next==NULL)
{
return NULL;
}
tempo=it->curr;
it->curr=it->curr->next;
// move to next node in list
return tempo->value;
}
我正在使用 Linux 环境，错误是从结果中看出的。这是整个程序的代码：
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include "iteratorG.h"
typedef struct Node {
void *value; // value of thee list item
struct Node *prev;
// pointer previous node in list
struct Node *next;
// pointer to next node in list
// implemented struct here ..
} Node;
typedef struct IteratorGRep {
int numofit; // count of items in list
Node *head; // first node in list
Node *curr; // current node in list
Node *tail; // last node in list
ElmCompareFp cmpElm;
ElmNewFp newElm;
ElmFreeFp freeElm;
// implemented struct here ..
} IteratorGRep;
/*
//Your functions below ....
*/
IteratorG newIterator(ElmCompareFp cmpFp, ElmNewFp newFp, ElmFreeFp freeFp){
IteratorG newit;
if ((newit = malloc(sizeof (struct IteratorGRep)))==NULL)
{
printf("Error...! \n");
}
//assert (newit != NULL);
newit->numofit = 0;
newit->head = NULL;
newit->tail = NULL;
newit->curr = NULL;
newit->cmpElm=cmpFp;
newit->newElm=newFp;
newit->freeElm=freeFp;
return newit;
// implemented function here and changed return value
}
int add(IteratorG it, void *vp){
Node *temp;
if ((temp = malloc(sizeof(Node))) == NULL) {
return 0;
}
temp->value = it->newElm(vp);
temp->next=NULL;
if(it->curr==NULL)
{
//temp->next=it->curr;
it->curr=temp;
it->tail=it->head=it->curr;
}
temp->next=it->curr;
it->curr->prev=temp;
it->curr=temp;
it->head=it->curr;
//it->curr->prev=temp;
/*temp->next = it->curr;
it->curr = temp;
*/
// add node to list from front
return 1;
}
int hasNext(IteratorG it){
if(it->curr->next==NULL)
{
return 0;
}
// check if theres next element/node
return 1;
}
int hasPrevious(IteratorG it){
if(it->curr->prev!=NULL)
{
return 1;
}
// check if theres previous element/node
return 0;
}
void *next(IteratorG it){
Node *tempo;
if ((tempo = malloc(sizeof(Node))) == NULL) {
return 0;
}
if(it->curr->next==NULL)
{
return NULL;
}
tempo=it->curr;
it->curr=it->curr->next;
// implemented function here
return tempo->value;
}
void *previous(IteratorG it){
Node *tempor;
if ((tempor = malloc(sizeof(Node))) == NULL) {
return 0;
}
tempor=it->curr;
if(tempor->prev==NULL)
{
return NULL;
}
tempor=it->curr->prev;
it->curr=it->curr->prev;
//tempor=it->curr;
// move to next node in list
return tempor->value;
}
int del(IteratorG it){
if(it->curr->prev!=NULL)
{
Node *temp_curr=it->curr;
Node *temp_prev=it->curr->prev->prev;
temp_curr->prev=temp_prev;
temp_prev->next=temp_curr;
return 1;
}// delete previous node from list
else
return 0;
}
int set(IteratorG it, void *vp){
if(it->curr->prev!=NULL)
{
it->curr->prev->value=vp;
/*
Node *wep;
if ((wep = malloc(sizeof(Node))) == NULL) {
return 0;
}
wep->value=it->newElm(vp);
store_next=it->curr;
store_prev=it->curr->prev->prev;
store_next->prev=wep;
wep->next=store_next;
store_prev->next=wep;
wep->prev=store_prev;
*/
return 1;
}
// change previous node value with new
return 0;
}
IteratorG advance(IteratorG it, int n){
//To be implemented
//move forward by n times
return NULL;
}
void reverse(IteratorG it){
Node *curr = it->head;
Node *temp = NULL;
while(curr != NULL) {
temp = curr->next;
curr->next = curr->prev;
curr->prev = temp;
curr = temp;
}
temp = it->head;
it->head = it->tail;
it->tail = temp;// reverse elements of whole list
}
IteratorG find(IteratorG it, int (*fp) (void *vp) ){
// To be implemented
// Find elements of vp in list after current position and put in new list.return the list.
return NULL;
}
int distanceFromStart(IteratorG it){
Node *c=it->curr;
int count=0;
while(c->prev!=NULL)
{
c=c->prev;
count++;
}
return count;
// count number of elements from start of list to current position
}
int distanceToEnd(IteratorG it){
Node *cu=it->curr;
int count=0;
while(cu->next!=NULL)
{
cu=cu->next;
count++;
}
return count;
// count number of elements from end of list to current position
}
void reset(IteratorG it){
while(it->curr->prev!=NULL)
{
it->curr=it->curr->prev;
}
return;
// move current position to start of list
}
void freeIt(IteratorG it){
assert(it != NULL);
Node *curr, *prev;
curr = it->head;
while (curr != NULL) {
prev = curr;
curr = curr->next;
free(prev->value);
free(prev);
}
free(it); // free items
}
这是代码的头文件：
#ifndef LISTITERATORG_H
#define LISTITERATORG_H
#include <stdio.h>
typedef struct IteratorGRep *IteratorG;
typedef int (*ElmCompareFp)(void const *e1, void const *e2);
typedef void *(*ElmNewFp)(void const *e1);
typedef void (*ElmFreeFp)(void *e1);
IteratorG newIterator(ElmCompareFp cmpFp, ElmNewFp newFp, ElmFreeFp freeFp);
int add(IteratorG it, void *vp);
int hasNext(IteratorG it);
int hasPrevious(IteratorG it);
void *next(IteratorG it);
void *previous(IteratorG it);
int del(IteratorG it);
int set(IteratorG it, void *vp);
IteratorG advance(IteratorG it, int n);
void reverse(IteratorG it);
IteratorG find(IteratorG it, int (*fp) (void *vp) );
int distanceFromStart(IteratorG it);
int distanceToEnd(IteratorG it);
void reset(IteratorG it);
void freeIt(IteratorG it);
#endif
其中一个功能尚未实现，并在代码中指明。但我想这可能不是问题的根源。我发现这里没有正确使用 NULL。
编辑： 这是测试用例代码。只有上面程序中的测试用例代码没有错误：
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include "iteratorG.h"
#include "positiveIntType.h"
#include "stringType.h"
#define MAXARRAY 5
/* Helper Functions Below */
/* Returns 1 if marks >= 50, 0 otherwise */
int passMarks(void *marks){
return (*((int *) marks) >= 50);
/* Easy to understand below ..
int *ip = (int *) marks;
if(*ip >= 50) { return 1; }
else { return 0; }
*/
}
/* Returns 1 if str starts with "jo" */
int prefixJo(void *str){
return (strncmp("jo", (char *) str, 2) == 0) ;
}
/* A function to print a string from a void pointer */
void prnStr(void *vp){
assert(vp != NULL);
printf(" %s", (char *) vp );
}
/* A function to print an integer from a void pointer */
void prnInt(void *vp){
assert(vp != NULL);
printf(" %d", *((int *) vp) );
}
/* Prints previous element using the given function 'fp'
examples: prnPrev(it1, prnInt); prnPrev(it2, prnStr);
*/
void prnPrev(IteratorG it, void (*fp) (void *p) ){
void *prevP = previous(it);
assert(prevP != NULL);
printf("> Previous value is: ");
fp(prevP);
printf("\n");
}
/* Prints next element using the given function 'fp'
examples: prnNext(it1, prnInt); prnNext(it2, prnStr);
*/
void prnNext(IteratorG it, void (*fp) (void *p) ){
void *nextP = next(it);
assert(nextP != NULL);
printf("> Next value is: ");
fp(nextP);
printf("\n");
}
/* Prints elements of 'it' from current to last position
using the given function 'fp'. The current position
of 'it' will change to the end of the list.
examples: prnIt(it1, prnInt); prnIt(it2, prnStr);
*/
void prnIt(IteratorG it, void (*fp) (void *p) ){
int count = 0;
while(hasNext(it)){
void *nextP = next(it);
count++;
if(count > 1) { printf(", "); }
fp(nextP);
}
printf("\n");
}
/* Few Tests Below */
void test1(){
printf("\n--==== Test-01 ====------\n");
IteratorG it1 = newIterator(positiveIntCompare, positiveIntNew, positiveIntFree);
int a[MAXARRAY] = { 25, 78, 6, 82 , 11};
for(int i=0; i<MAXARRAY; i++){
int result = add(it1 , &a[i]);
printf("> Inserting %d: %s \n", a[i], (result==1 ? "Success" : "Failed") );
}
freeIt(it1);
printf("--==== End of Test-01 ====------\n");
}
void test2(){
printf("\n--==== Test-02 ====------\n");
IteratorG it1 = newIterator(positiveIntCompare, positiveIntNew, positiveIntFree);
int a[MAXARRAY] = { 72, 14, 62, 8, 93};
for(int i=0; i<MAXARRAY; i++){
int result = add(it1 , &a[i]);
printf("> Inserting %d: %s \n", a[i], (result==1 ? "Success" : "Failed") );
}
prnNext(it1, prnInt);
prnNext(it1, prnInt);
prnPrev(it1, prnInt);
int newVal1 = 55;
int result1 = set(it1, &newVal1);
printf("> Set value: %d ; return val: %d \n", newVal1, result1 );
prnPrev(it1, prnInt);
freeIt(it1);
printf("--==== End of Test-02 ====------\n");
}
int main(int argc, char *argv[])
{
test1();
test2();
return EXIT_SUCCESS;
}
在add函数中，第一次添加时，it->curr是null，它使temp->next指向它自己，而不是null，所以链表似乎没有尽头:
您的原始代码：
if(it->curr==NULL)
{
it->curr=temp; // the current element is the add element
it->tail=it->head=it->curr;
}
temp->next=it->curr; // for the first element, it->curr is already valued to temp : temp->next points to temp :(
add 函数可以是：
// add node to list from front
int add(IteratorG it, void *vp){
Node *temp;
if ((temp = malloc(sizeof(Node))) == NULL) {
return 0;
}
temp->value = it->newElm(vp);
temp->prev = null;
temp->next = it->curr;
if (it->curr != NULL)
it->curr->prev = temp;
it->curr = temp;
it->head = it->curr;
return 1;
}
此外，我知道这不是您要的，但是 丑陋的 内存泄漏 next 和 previous 函数...