99瓶啤酒遞歸似乎不起作用

Question

好的，這裏是我在學習過程中編寫的簡單代碼。

void SingTheSong (int NumOfBottles) 
{ 
    if (NumOfBottles == 0){ 
     printf("there are simply no more bottles of beer on the wall. \n"); 
    } 

    else { 
     printf("%d bottles of beer on the wall, %d bottles of beer.\n", NumOfBottles, NumOfBottles); 
     int Bottleless = NumOfBottles - 1; 
     printf("Take one down pass it around, %d bottles of beer on the wall. \n", Bottleless); 

     SingTheSong(Bottleless); 
     printf("Put a bottle in the recycling bin, there are now %d empty bottles in the bin.\n", NumOfBottles); 
    } 
} 

int main(int argc, const char * argv[]) 
{ 
    SingTheSong(99); 
    return 0; 
} 

我無法理解的事情就是爲什麼在1 SingTheSong（Botteless）功能啓動時的程序運行，爲什麼它顯示的printf（）語句後有啤酒在0瓶壁。只是一個混亂，因爲我認爲在else語句再次運行else語句之前，大括號內的所有內容都在else語句中被引用。爲什麼不是這樣？

例：在牆壁上 「99瓶啤酒，99瓶啤酒以一個向下，圍繞通過它，98瓶的上壁啤酒 將一個瓶的回收箱，現在有1空瓶子在箱子裏「 」98瓶啤酒在牆上，98瓶啤酒。取下一個，繞過它，在牆上的97瓶啤酒 把一瓶放在回收桶裏，現在有2瓶在空箱裏的空瓶子「

我知道他是初學者，我是初學者。有人可以向我解釋這一點，所以我停止在圈子裏。謝謝！

Answer 1

您正在遞交的SingTheSong函數之前您的printf關於回收箱中的瓶子數量。

回收箱邏輯中還存在一個缺陷 - 您需要將回收箱中的瓶子當前數量遞歸地傳遞給您的函數 - 現在的方式，如果您將線條的順序修改爲如上所述，它將總是打印比在垃圾箱中的壁上的瓶子總數少一個。

下面是一些僞代碼，以顯示這種遞歸的應該是什麼樣子：

function singTheSong(bottlesOnWall,bottlesInBin) { 
    if (bottlesOnWall == 0) { 
     print("There are no more bottles.\n"); 
    } else { 
     printf("%d bottles of beer on the wall, %d bottles of beer.\n", bottlesOnWall, bottlesOnWall); 
     bottlesOnWall--; 
     bottlesInBin++; 
     printf("Take one down pass it around, %d bottles of beer on the wall.\n", bottlesOnWall); 
     printf("Put a bottle in the recycling bin, there are now %d empty bottles in the bin.\n", bottlesInBin); 
     singTheSong(bottlesOnWall,bottlesInBin); 
    } 
} 

singTheSong(99,0); 

Answer 2

嗯，我不明白的地方你面臨的問題，但在這裏不用解釋：

對於NumOfBottles = 99：

printf("%d bottles of beer on the wall, %d bottles of beer.\n", NumOfBottles, NumOfBottles); // = 99 bottles of beer on the wall, 99 bottles of beer. 
int Bottleless = NumOfBottles - 1; // 98 
printf("Take one down pass it around, %d bottles of beer on the wall. \n", Bottleless); //98 bottles of beer on the wall. 
SingTheSong(98) 

爲NumOfBottles = 98：

printf("%d bottles of beer on the wall, %d bottles of beer.\n", NumOfBottles, NumOfBottles); //= 98 bottles of beer on the wall, 98 bottles of beer 
int Bottleless = NumOfBottles - 1; // 97 
printf("Take one down pass it around, %d bottles of beer on the wall. \n", Bottleless); //97 bottles of beer on the wall 
SingTheSong(97); 

...

在結束時NumOfBottles = 0： 的printf（「有啤酒在牆壁上根本就沒有更多的瓶子。 。\ n「）; //有簡單的牆上啤酒沒有更多的瓶子//現在回到

現在，這將是印刷99次：

printf("Put a bottle in the recycling bin, there are now %d empty bottles in the bin.\n", NumOfBottles);//starting from 1 upto 99. 

這就是爲什麼它不喜歡的！是，因爲遞歸函數調用前是printf("Put a bottle...")

解決方案：

void SingTheSong (int NumOfBottles) 
{ 
    if (NumOfBottles == 0){ 
     printf("there are simply no more bottles of beer on the wall. \n"); 
    } 


    else { 
     printf("%d bottles of beer on the wall, %d bottles of beer.\n", NumOfBottles, NumOfBottles); 
     int Bottleless = NumOfBottles - 1; 
     printf("Take one down pass it around, %d bottles of beer on the wall. \n", Bottleless); 
     printf("Put a bottle in the recycling bin, there are now %d empty bottles in the bin.\n", 99-Bottleless); 
     SingTheSong(Bottleless); 
    } 
} 

Answer 3

試想一下，你知道什麼SingTheSong爲方法打印。現在分開交易if聲明的兩個分支。當NumOfBottles爲零時，打印「no bottles」消息並返回。當NumOfBottles不爲零，我們做以下三兩件事：瓶

• 打印數量N
• 打印任何SingTheSong爲N-1
• 打印回收信息方法打印N

的中間行是遞歸：它可以擴展爲相同的三行，如下所示：

• 打印瓶N數量
• 打印瓶N-1數量
• 打印任何SingTheSong爲N-2
• 打印回收消息N-1
• 打印回收消息方法打印N

你可以d一次又一次，直到中間線變成「脫啤酒」的信息。

Answer 4

沒有完整的答案。只是顯示你可能想補充其他答案。

void SingTheSong (int bottlesOnWall, int bottlesInBin) 
{ 
    if (bottlesOnWall == 0){ 
     printf("there are simply no more bottles of beer on the wall. \n"); 
    } 

    else { 
     printf("%d bottles of beer on the wall, %d bottles of beer.\n",bottlesOnWall, bottlesOnWall); 
     printf("Take one down pass it around, %d bottles of beer on the wall. \n", --bottlesOnWall); 
     printf("Put a bottle in the recycling bin, there are now %d empty bottles in the bin.\n", ++bottlesInBin); 

     SingTheSong(bottlesOnWall, bottlesInBin); 
    } 
} 

開始，您可以調用的功能等：

SingTheSong(99, 0); 

此外，你可能想了解更多關於recursion。

Answer 5

這是一個函數遞歸，當您啓動SingTheSong（無邊距）表單99到1時，它將調用無邊距爲99,98,97 ......的函數...... 1.在SingTheSong（1）之後，然後繼續執行printf \ n「，NumOfBottles）;」將一個瓶子放在回收桶中，現在有％d個空瓶子在瓶子裏。\ n「，NumOfBottles）;」

然後回到SingTheSong（2），因爲它的推移，終於回來SingTheSong（99）