如何為列表中的每個第二個節點添加值

Question

我嘗試遍歷值的鏈接列表，並將一些給定值添加到列表中的每個其他節點。 它應該總是開始添加到列表中的第一個節點，然后從那里添加到每個其他節點。

錯誤是程序沒有給出任何 output 但它很可能是 function 有問題

這是我嘗試過的：

#include <iostream>
using namespace std;

// Declare the Node structure to be used for the linked list.
// Each node should have an int for data, and
// a pointer to the next node.
struct Node {
   int data;
   Node *pNext;
};

// Displays the list number values
void display( Node *pTemp){
    while( pTemp != NULL) {
        cout << pTemp->data << "->";
        pTemp = pTemp->pNext;
    }
    cout << endl;
}

// Create a new node, put the userInput number in it, and APPEND
// it to the END of the list.
void append(Node* &pHead, int userInput) {
    Node *pTemp = new Node;
    pTemp->data = userInput;
    pTemp->pNext = NULL;

    Node *pLast = pHead;
    // Find the last node on the list
    while(pLast != NULL && pLast->pNext != NULL) {
        pLast = pLast->pNext;
    }

    if( pLast == NULL) {
        // Make this new node the first node on an otherwise empty list
        pHead = pTemp;
    }
    else {
        // Append this new node to the end of the existing list
        pLast->pNext = pTemp;
    }
}

//-----------------------------------------------------------------------
//       *** Do not change anything above this point. ***
//------------------------------------------------------------------------ 

// add valueToAdd to every second node in the list
void addEveryOther(Node* &pHead, int valueToAdd) {
    
    // while there is a node after pTemp->pNext
    while(pHead->pNext != NULL || pHead != NULL) {
        // add valueToAdd to pTemp->data
        pHead->data += valueToAdd;
        // move pTemp to the next node
        pHead = pHead->pNext->pNext;
    }
}

//-----------------------------------------------------------------------
//       *** Do not change anything below this point. ***
//------------------------------------------------------------------------

int main() {
   int userInput;
   Node *pHead = NULL;  // pointer to the head of the list
   int value;
   
   // Create the linked list
   cout << "Enter list numbers separated by space, followed by -1: ";
   cin >> userInput;

   // Keep looping and appending nodes on the list until 
   // end-of-input flag of -1 is given
   while(userInput != -1) {
        // Store this number on the list
        append(pHead, userInput);
        cin >> userInput;
    }

    cout << "Enter value to add on: ";
    cin >> value;
    addEveryOther(pHead, value);
    display(pHead);

    return 0;

}// end main()

這是輸入：

2 8 9 5 11 3 6 -1
Enter value to add on: 5

預計 output：

7->8->14->5->16->3->11

Answer 1

您需要考慮做事的順序。 以及您的條件中的邏輯。

在條件pHead->pNext != NULL || pHead != NULL pHead->pNext != NULL || pHead != NULL在檢查它是否為 null 指針之前，您將取消引用pHead 。

您需要以相反的順序進行檢查，並使用邏輯 AND 代替： pHead != NULL && pHead->pNext != NULL 。