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

Golang:

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
}

Explanation Link to heading

Number of letters are 26 from ‘a’ to ‘z’. We can use array as a cache instead of map to improve performance. All we need is to increment magazine inventory and decrement characters in note.