383. Ransom Note

二刷 08/2022

Version #1 Array as counter map

Time O(M + N)

Space O(1)

Runtime: 5 ms, faster than 74.47% of Java online submissions for Ransom Note.

Memory Usage: 44.8 MB, less than 85.10% of Java online submissions for Ransom Note.

class Solution {

    public boolean canConstruct(String ransomNote, String magazine) {

        int[] count = new int[26];

        for (int i = 0; i < magazine.length(); i++) {

            count[magazine.charAt(i) - 'a']++;

        }

        for (int i = 0; i < ransomNote.length(); i++) {

            if (--count[ransomNote.charAt(i) - 'a'] < 0) {

                return false;

            }

        }

        return true;

    }

}

一刷

对于 “” “” 的情况要在最后判断一下

 61.66 %

class Solution {
    public boolean canConstruct(String ransomNote, String magazine) {
        if (ransomNote == null || magazine == null) return false;
        int[] counter = new int[256];
        int match = 0;
        for (int i = 0; i < ransomNote.length(); i++) {
            counter[ransomNote.charAt(i)]++;
            match++;
        }
        for (int j = 0; j < magazine.length(); j++) {
            if (counter[magazine.charAt(j)] > 0) {
                counter[magazine.charAt(j)]--;
                match--;
            }
            if (match == 0) return true;
        }
        return match == 0;
    }
}