1160. Find Words That Can Be Formed by Characters

Problem

You are given an array of strings words and a string chars.

A string is good if it can be formed by characters from chars (each character can only be used once).

Return the sum of lengths of all good strings in words.

  Example 1:

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.

Example 2:

Input: words = ["hello","world","leetcode"], chars = "welldonehoneyr"
Output: 10
Explanation: The strings that can be formed are "hello" and "world" so the answer is 5 + 5 = 10.

  Constraints:

• 1 <= words.length <= 1000

• 1 <= words[i].length, chars.length <= 100

• words[i] and chars consist of lowercase English letters.

Solution (Java)

class Solution {
    public int countCharacters(String[] words, String chars) {
        int length = 0;
        Map<Character, Integer> map = new HashMap<>();
        for (char c : chars.toCharArray()) {
            int count = map.getOrDefault(c, 0);
            map.put(c, count + 1);
        }
        for (String word : words) {
            if (canForm(word, map)) {
                length += word.length();
            }
        }
        return length;
    }

    private boolean canForm(String word, final Map<Character, Integer> map) {
        Map<Character, Integer> tmp = new HashMap<>(map);
        for (Character c : word.toCharArray()) {
            if (tmp.containsKey(c) && tmp.get(c) > 0) {
                int count = tmp.get(c);
                tmp.put(c, count - 1);
            } else {
                return false;
            }
        }
        return true;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).