创建含25-75个0-100随机数的Linked List无输出问题求助

问题描述 #

需要创建包含25至75个0-100之间随机整数的链表并显示，但运行程序后控制台无输出、无报错且无法自行结束。期望输出示例：

Ex. The list is: 0, 0, 1, 4, 5, 6, 8, 9, 12, 13, 14, 17, 19, 20, 20, 23, 24, 25, 25, 26, 28, 30, 30, 32, 34, 36, 37, 38, 43, 44, 46, 50, 53, 54, 54, 62, 62, 65, 66, 66, 68, 70, 70, 74, 79, 79, 80, 82, 83, 85, 85, 89, 96, 97,

问题分析与修正 #

1. 无限循环的核心错误 #

main函数中的for循环条件误用了赋值操作而非比较操作：

// 错误写法
for(i = 0; i = listcount-1; i++){

i = listcount-1会将listcount-1的值赋给i，该表达式结果永远为真（listcount最小为25，listcount-1不为0），导致循环无限执行，程序永远无法走到display函数。

修正为：

// 正确写法：循环listcount次
for(i = 0; i < listcount; i++){

或等价的i <= listcount-1。

2. 插入逻辑与期望输出不符 #

当前insert函数的while循环条件num2 <= current->data会生成降序列表，与用户期望的升序输出不符。需将条件改为num2 >= current->data，这样才能找到第一个大于当前数值的节点，将新节点插入其前方，实现升序排列。

修正后的insert函数核心部分：

// 修正条件，实现升序插入
while(NULL != current && num2 >= current->data){
  previous = current;
  current = current->next;
}//end of while

修正后的完整代码 #

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

//Self Referential Structure
struct node{
  int data;
  struct node *next;
};

//Type Definitions
typedef struct node Node;
typedef struct node* NodePointer;

//Function Prototypes
void insert(int, NodePointer *);
void display(NodePointer);

//Insert Function
void insert(int num2, NodePointer *head2){
  NodePointer newNode = NULL;
  NodePointer previous = NULL;
  NodePointer current = *head2;

  newNode = malloc(sizeof(Node));
  if(NULL != newNode){
    newNode->data = num2;
    // 修正条件，实现升序插入
    while(NULL != current && num2 >= current->data){
      previous = current;
      current = current->next;
    }//end of while
    if(NULL == previous){
      newNode->next = current;
      *head2 = newNode;
    }//end of if
    else{
      previous->next = newNode;
      newNode->next = current;
    }//end of else
  }//end of if
}//end of function

//Display Function
void display(NodePointer current){
  if(NULL == current){
    printf("The linked list is empty!\n\n");
    return;
  }
  printf("The list is: ");
  while(NULL != current){
    printf("%i, ", current->data);
    current = current->next;
  }
  printf("\n\n");
}

//MAIN FUNCTION
int main(){
  int i = 0;
  int listcount = 0;
  int num = 0;

  NodePointer head = NULL;

  srand(time(NULL));
  listcount = rand() % (75 + 1 - 25) + 25;
  
  // 修正循环条件，避免无限循环
  for(i = 0; i < listcount; i++){
    num = rand() % 100;
    insert(num, &head);
  }

  display(head);

  return 0;
  
}

内容的提问来源于stack exchange，提问作者Erin