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.
Update: It was troubling me that I couldn't get a higher result, and since JS gives us many ways of doing the same thing I decided to try one more time.
Now with a 90th percentile + result, I'm much happier :-)
// Runtime: 64 ms, faster than 94.72% of JavaScript online submissions for Ransom Note.
// Memory Usage: 38.4 MB, less than 33.33% of JavaScript online submissions for Ransom Note.
var canConstruct = function(ransomNote, magazine) { if (ransomNote.length > magazine.length) return false; let charMap = []; for (let i = 0; i < ransomNote.length; i++) { if (magazine.indexOf(ransomNote[i]) == -1) return false; let char = ransomNote.codePointAt(i); charMap[char] = charMap[char] - 1 || -1; } for (let i = 0; i < magazine.length; i++) { let char = magazine.codePointAt(i); charMap[char] = charMap[char] + 1 || 1; } for (const charCount of charMap) if (charCount < 0) return false; return true; }; ** previously **
Didn't get a particularly impressive result, but here's 3 valid solutions exploring different data structures and approaches.
// Runtime: 76 ms, faster than 77.31% of JavaScript online submissions for Ransom Note.
// Memory Usage: 38.1 MB, less than 33.33% of JavaScript online submissions for Ransom Note
var canConstruct = function(ransomNote, magazine) { let retVal = true; const noteCharMap = [...ransomNote].reduce((acc, val, _, arr) => { acc[val] = acc[val] + 1 || 1; if (magazine.indexOf(val) == -1) { retVal = false; arr.pop(); //force early return with arr mutation } return acc; }, {}); if (!retVal) return false; const magzCharMap = [...magazine].reduce((acc, val) => { acc[val] = acc[val] + 1 || 1; return acc; }, {}); for (const [char, count] of Object.entries(noteCharMap)) { if (magzCharMap[char] < count) return false; } return true; }; var canConstruct = function(ransomNote, magazine) { let charMap = {}; for (const char of ransomNote) { if (magazine.indexOf(char) == -1) return false; charMap[char] = charMap[char] + 1 || 1; } for (const char of magazine) { if (charMap[char]) charMap[char] -= 1; if (charMap[char] == 0) delete charMap[char]; } for (const _ in charMap) return false; return true; }; var canConstruct = function(ransomNote, magazine) { const charMap = new Map(); for (const char of ransomNote) { if (magazine.indexOf(char) == -1) return false; charMap.set(char, charMap.get(char) + 1 || 1) } for (const char of magazine) { charMap.set(char, charMap.get(char) - 1 || 0) if (charMap.get(char) <= 0) charMap.delete(char); } for (const _ of charMap) return false; return true; }; 
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