如何检查Java中另一个String的字符是否可以组成一个String？

Question

A string is good if it can be formed by characters from chars. I want to return the sum of lengths of all good strings in words.

Input: words = ["cat","bt","hat","tree"], chars = "atach"

Output: 6

Explanation: The strings that can be formed are "cat" and "hat" so the answer is 3 + 3 = 6.

Below is the code that I have written.

class Solution
{
    public int countCharacters(String[] words, String chars) 
    {
        int k = 0, count = 0;
        Set<Character> set = new HashSet<>();
        for(int i = 0; i < chars.length(); i++)
        {
            set.add(chars.charAt(i));
        }

        StringBuilder chrs = new StringBuilder();
        for(Character ch : set)
        { 
            chrs.append(ch);   
        }

        for(int i = 0; i < words.length; i++)
        {
            char[] ch = words[i].toCharArray();

            for(int j = 0; j < ch.length; j++)
            {
                if(chrs.contains("" + ch[j]))
                {
                    k++;
                }
            }

            if(k == words[i].length())
            {
                count+= k;
            }
        }

        return count;
    }
}

Output:
Line 24: error: cannot find symbol

                if(chrs.contains("" + ch[j]))

Can someone help me? What am I doing wrong in accessing the character?

Answer 1

contains tells you if a string is contained in another string . But in your case ch[j] is not a string but a char, so you can't use contains .

Instead, use indexOf , it returns -1 if the char is not present in the string.

Answer 2

the most simple way is

chars.contains("" + ch[i]);

Answer 3

Here, ch[j] is not a string but a char, so you can't use contains as you've done. Instead, make the following change.

chars.contains(String.valueOf(ch[j]));

Answer 4

The issues which I noticed is you are using contains() to compare a String and a character. But the contains() method is a Java method to check if String contains another substring or not.

So you can solve this by converting the character to a string.

Ex 1:

if(chars.contains(Character.toString(ch[j]))){
    k++;
} else {
}

Ex 2:

f(chars.contains(""+ch[j]))
{
    k++;
} else {
}

Otherwise, You can compare if the string contains a char by using indexOf() . If the string isn't containing the char it return -1. Please refer bellow example.

Ex:

if(chars.indexOf(ch[j])!=-1){
    k++;
} else {
}