java使用遞歸查找字符串中的子串

Question

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/** 
     Recursive method for looking for a substring in a string. 
     @param text look in 
     @param target look for as substring 
     @return true if target is a substring of text 
    */ 
    public static boolean find(String text, String target) 
    { 
     //-----------Start below here. To do: approximate lines of code = 4 
     // 1. base case: null 
     if (text == null) {return false;}   
     //2. base case: target too long 
     if (target.length() > text.length()) {return false;} 
     //3. base case: same length 
     if (text.length() == target.length()) {return false;} 
     //4. base case: startsWith OR 5. recursive case 
     return true; 
    } 

Answer 1

試試這個

/** 
Recursive method for looking for a substring in a string. 
@param text look in 
@param target look for as substring 
@return true if target is a substring of text 
*/ 
public static boolean find(String text, String target) 
{ 
//-----------Start below here. To do: approximate lines of code = 4 
// 1. base case: null 
if (text == null || target == null) {return false;} // added target null check  
//2. base case: target too long 
if (target.length() > text.length()) {return false;} 
//3. base case: same length 
if (text.length() == target.length()) {return text.equals(target);} 
//4. base case: startsWith OR 5. recursive case 
return text.startsWith(target) || find(text.substring(1) , target); 
}