Java中两个字符串的交集

Question

需要一个Java函数来查找两个字符串的交集.即字符串共有的字符.

例:

String s1 = new String("Sychelless");
String s2 = new String("Sydney");

Answer 1

使用HashSet<Character>:

HashSet<Character> h1 = new HashSet<Character>(), h2 = new HashSet<Character>();
for(int i = 0; i < s1.length(); i++)                                            
{
  h1.add(s1.charAt(i));
}
for(int i = 0; i < s2.length(); i++)
{
  h2.add(s2.charAt(i));
}
h1.retainAll(h2);
Character[] res = h1.toArray(new Character[0]);

这是O(m + n)渐近最优的.

Answer 2

提取字符

String.toCharArray

将它们放入Set Set the intersection中

Set.retainAll

Answer 3

最基本的方法:

String wordA = "Sychelless";  
String wordB = "Sydney";  
String common = "";  

for(int i=0;i<wordA.length();i++){  
    for(int j=0;j<wordB.length();j++){  
        if(wordA.charAt(i)==wordB.charAt(j)){  
            common += wordA.charAt(i)+" ";  
            break;
        }  
    }  
}  
System.out.println("common is: "+common);