Ransom Note

Introduction Link to heading

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.

Each letter in the magazine string can only be used once in your ransom note.

Note: You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true

Solution Link to heading

We can construct ransom note only if we have characters in magazine. So, the simple cache can help keep count positive.

func canConstruct(ransomNote string, magazine string) bool {
    cache := make([]int, 26)
    for  _, c := range magazine {
        cache[c-'a']++
    }
    for _, c := range ransomNote {
        v := cache[c - 'a']
        v--
        cache[c - 'a'] = v
        if v < 0 {
            return false
        }
    }
    return true
}