Java數組和循環導致錯誤輸出

Question

需求是檢查數組中的重複項並刪除它，數組中的其餘項必須移到左邊。

我寫了這個：

public class TestRepeat { 

public static int deleteRepeats(char[] ch) { 

    int count = 0; 
    for (int x = 0; x < ch.length; x++) { 
     for (int y = x + 1; y < ch.length; y++) { 
      if (ch[x] == ch[y]) { 
       for (int k = y; k < ch.length - 1; k++) {//shifts the array to the right if its a duplicate 
        ch[k] = ch[k + 1]; 
       } 
       ch[ch.length - 1] = ' ';//replaces the last array with a blank 
      } 
     } 
    } 
    for (int q = 0; q < ch.length; q++) { 
     if (ch[q] == ' ') { 
      count++; 
     } 
    } 
    return count;//returns the number of deleted items 
} 

public static void main(String[] args) { 
    char[] ch = {'k', 'a', 'm', 'o', 'k', 'm', 'y', 'm', 'k', 'k', 'x', 'm', 'm', 'o'}; 
    System.out.print("The original array is: "); 
    System.out.println(ch); 
    System.out.println("Number of deleted characters: " + deleteRepeats(ch)); 
    System.out.print("The new array is: "); 
    System.out.println(ch); 
} 

} 

它應該返回：

原始數組：kamokmymkkxmmo

刪除字符數：8

新的陣列：kamoyx

而是將返回：

原始數組：kamokmymkkxmmo

刪除字符數：6

新數組是：kamoykxm

是什麼原因造成的問題，我該如何解決它？

Answer 1

我發現了兩個錯誤，其中一個導致了你的問題，另一個導致了錯誤。首先，你不能在內循環中使用for循環，因爲有時你正在修改你正在循環的數組。因此，在一些迭代中，你隱式地增加y兩次：一次通過實際增加y，並且再次將數組的一部分移到左側。因此，當您不對數組執行更改時，實際上應該增加y，並且在刪除元素時將y保留在原來的位置。其次，你必須確保你不要試圖刪除' '，因爲它會在while循環版本中導致無限遞歸。錯誤修復如下：

public class TestRepeat { 

/** Deletes index index in arr. Elements in (index, arr.length) are shifted to the left, 
    And a ' ' is put at the end of arr 
    Precondition: index >= 0, index < arr.length */ 
private static void deleteAndShift(char[] arr, int index){ 
    for(int i = index; i < arr.length - 1; i++){ 
     arr[i] = arr[i+1]; 
    } 
    arr[arr.length - 1] = ' '; 
} 

public static int deleteRepeats(char[] ch) { 

    int count = 0; 
    for (int x = 0; x < ch.length; x++) { 
     int y = x+1; 
     while(y < ch.length){ 
      //Delete index y. Note that this 'implicitly' increments y by shifting ch. 
      if (ch[x] != ' ' && ch[x] == ch[y]) { 
       deleteAndShift(ch, y); 
      } 
      //Only increment y if an element wasn't deleted 
      else{ 
       y++; 
      } 
     } 
    } 
    for (int q = 0; q < ch.length; q++) { 
     if (ch[q] == ' ') { 
      count++; 
     } 
    } 
    return count;//returns the number of deleted items 
} 

public static void main(String[] args) { 
    char[] ch = {'k', 'a', 'm', 'o', 'k', 'm', 'y', 'm', 'k', 'k', 'x', 'm', 'm', 'o'}; 
    System.out.print("The original array is: "); 
    System.out.println(ch); 
    System.out.println("Number of deleted characters: " + deleteRepeats(ch)); 
    System.out.print("The new array is: "); 
    System.out.println(ch); 
} 

} 

此代碼具有您希望的輸出樣本輸入中刪除8個字符。

Answer 2

更換if條件塊if (ch[x] == ch[y]) {用，

if (ch[x] != ' ' && ch[x] == ch[y]) {     
    for (int k = y; k < ch.length - 1; k++) {//shifts the array to the right if its a duplicate      
     ch[k] = ch[k + 1]; 
    }      
    ch[ch.length - 1] = ' ';//replaces the last array with a blank 
    y--; 
} 

Answer 3

後您將它們轉移到左側，做一個y--; 這將有助於照顧連續的重複元素

Answer 4

在set的幫助下，我們可以輕鬆實現它。

char[] ch = {'k', 'a', 'm', 'o', 'k', 'm', 'y', 'm', 'k', 'k', 'x', 'm', 'm', 'o'}; 
System.out.print("The original array is : "); 
System.out.println(ch); 

// Moving in to LinkedHashSet 
Set<Character> charSet = new LinkedHashSet<Character>(); 
for(char c : ch) 
    charSet.add(c); 

System.out.println("Number of deleted characters :"+(ch.length-charSet.size())); 

// Move Back to newArray 
char[] newch = new char[charSet.size()]; 
int i = 0; 
for(char c : charSet) 
    newch[i++] = c; 

System.out.print("The new array is :"); 
System.out.println(newch); 

輸出：

The original array is : kamokmymkkxmmo 
Number of deleted characters :8 
The new array is :kamoyx