布爾分類插入函數檢查如果int已經存在列表中

Question

我想實現一個接收List和Int作爲參數的bool函數，並且應該插入int並返回true，如果int不存在於列表中，或者false if它已經存在了，我已經使用這個函數工作了幾個小時，並且if-else語句可以插入sorted int，問題（和崩潰）是如何檢查該值是否已經存在並返回false，這裏是我的函數： 聲明結構

typedef struct E_Type * List; 
struct E_Type 
{ 
    int data; 
    List next = 0; 
}; 

和功能

bool insert(List & l, int data) 
{ 

    List current = l; 
     do{//check if the int is already in the list 
      current->data; 
      current = current->next; 
     //return false; 
    }while (current->data == data); 

     if (l == 0 || l->data > data){ 
       List new_list = new E_Type; 
       new_list->data = data; 
       new_list->next = l; 
       l = new_list; 
      return true; 
     } 

     else if(l->data < data){ 
      insert(l->next, data); 
      return true; 
    } 



    } 

的

Answer 1

do{ 
     //this line doesn't really do anything... 
     current->data; 
     //moving current forward, good. 
     current = current->next; 
//If current->data is less than data in the list, it will exit the loop here anyway. 
}while (current->data == data); 

您還沒有檢查您是否已到達列表的末尾。也許你正在試圖做的是這樣的：

//This is correct for for iterative approach, but I don't think this is really what you need, either... 
while(current != null) { 
    if (current->data == data) 
     return false; 
    current = current->next; 
} 

然而，你可能不希望使用迭代這樣做此檢查在遞歸函數，所以反而，只需更換與整個位：

if (current->data == data) 
    return false; 

，並返回通過遞歸調用正確的值，你會想改變：

else if(l->data < data){ 
    insert(l->next, data);   //Recursive call 
    return true; //you don't want to just return true, return what the recursive call returns! 
} 

要：

else if(l->data < data){ 
    return insert(l->next, data); 
}