比較字符串數組和字符串二分法查找

Question

計劃從排序字符串的txt文件讀取和使用順序，反覆二進制和遞歸二進制數組存儲然後搜索數組中的位置和多少次迭代花了查找的單詞。嘗試將數組中的單詞與用戶輸入的單詞進行比較時發生錯誤。不知道爲什麼。 2）希望有人能解釋迭代二進制和遞歸二進制之間的差異。 3）爲什麼必須做到這一點...

SearchString在SI =新SearchString在（）;

程序下面是...

import ... 

public class SearchString 
{ 
public static final String TO_STOP = "-1"; 
public static final int NOT_FOUND = -1; 
public static final int MAX_SIZE = 15000; 

    public static int count1; 
    public static int count2; 
    public static int count3; 


    public int sequentialSearch(String[] wordsArray, String word2Search) 
    { 
    int low = 0; 
    int high = wordsArray.length - 1; 
    for (int i = low; i <= high; i++) 
    { 
     count1++; 
     if (wordsArray[i] == word2Search) 
      return i; 
    } 
    return NOT_FOUND; 
    } // end of sequentialSearch() 

    public int binarySearch(String[] wordsArray, String word2Search) 
    { 
    int low = 0; 
    int high = wordsArray.length - 1; 
    while (low <= high) 
    { 
     int mid = (low + high)/2; 
     count2++; 
     if (wordsArray[mid] > word2Search){ 
      high = mid - 1; 
     } else if (wordsArray[mid] < word2Search){ 
      low = mid + 1; 
     } else 
      return mid; 
    } 
    return NOT_FOUND; 
    }/


    public int binarySearch2(String[] wordsArray, int low, int high, String word2Search){ 
    if (low > high) 
     return NOT_FOUND; 
    int mid = (low + high)/2; 
    count3++; 
    if (wordsArray[mid] > word2Search){ 
     return binarySearch2(wordsArray, low, mid-1, word2Search); 
    } else if (wordsArray[mid] < word2Search){ 
     return binarySearch2(wordsArray, mid+1, high, word2Search); 
    } else 
     return mid; 
    } 



public static void main(String[] args) throws IOException 
{ 
    Scanner keyboard = new Scanner(System.in); 

    boolean wantToContinue = true; 

    Scanner stringsFile = new Scanner (new File("sortedStrings.txt"));//.useDelimiter(",\\s*"); 
    List<String> words = new ArrayList<String>();   

    String token1 = "";          

    (stringsFile.hasNext())       
    {  token1 = stringsFile.next(); 
      words.add(token1); 
    } 
    stringsFile.close();          
    String[] wordsArray = words.toArray(new String[0]);  

    System.out.println(Arrays.toString(wordsArray)); 

    SearchString si = new SearchString(); 

    do { 
     System.out.print("Type a word to search or -1 to stop: "); 
     String word2Search = keyboard.nextLine(); 
     if (word2Search.equals(TO_STOP)){ 
      wantToContinue = false; 
     } else { 
      count1 = count2 = count3 = 0; 
      int index; 

      index = si.sequentialSearch(wordsArray, word2Search); 
      if (index == NOT_FOUND) 
       System.out.println("sequentialSearch()  : " + word2Search + " is not found (comparison=" + count1 + ")."); 
      else 
       System.out.println("sequentialSearch()  : " + word2Search + " is found in [" + index + "] (comparison=" + count1 + ")."); 

      index = si.binarySearch(wordsArray, word2Search); 
      if (index == NOT_FOUND) 
       System.out.println("iterative binarySearch(): " + word2Search + " is not found (comparison=" + count2 + ")."); 
      else 
       System.out.println("iterative binarySearch(): " + word2Search + " is found in [" + index + "] (comparison=" + count2 + ")."); 

      index = si.binarySearch2(wordsArray, 0, wordsArray.length-1, word2Search); 
      if (index == NOT_FOUND) 
       System.out.println("recursive binarySearch(): " + word2Search + " is not found (comparison=" + count3 + ")."); 
      else 
       System.out.println("recursive binarySearch(): " + word2Search + " is found in [" + index + "] (comparison=" + count3 + ")."); 
     } 
    } while (wantToContinue); 

} 

}

Answer 1

你不能比較String與==（或>和<）。您需要使用 String.compareTo

Answer 2

如何比較String S（或任何其他類型的Comparable對象）：

• a > b成爲a.compareTo(b) > 0
• a < b成爲a.compareTo(b) < 0
• a == b成爲a.equals(b)