383. Ransom Note | LeetCode Solution | JavaScript | Easy

LeetCode Problem - Link

I will be solving the Ransom Note problem from LeetCode today, this requires you to utilize a hashmap to solve this. I took a while to solve this perfectly, I spent almost 20 minutes trying to create 2 hashes (god knows for what) and compare them. Took a break, and came back later to get an idea that a single hash map is enough, which emphases that programmers need breaks and I need to remind myself consistently to take breaks when I'm stuck with something. Changing the way you think and attacking a problem from multiple angles is the key to solving them

Hashmaps are pretty useful, it took me a long time (a couple of years) to get used to/comfortable or even understand what a hashmap is. Not until I became a full-time JavaScript developer that I started to think about data in terms of objects.

Simple Hashmap Solution

/**
 * @param {string} ransomNote
 * @param {string} magazine
 * @return {boolean}
 */


var buildMapFromString = (string) => {
    // utility function that helps us build a map with count values
    var map = {}
    var arr = string.split('')
    for (var i = 0; i < arr.length; i++) {
        var stringChar = arr[i]
        if (map[stringChar]) {
            map[stringChar] += 1
        } else {
            map[stringChar] = 1
        }
    }
    return map
}


var canConstruct = function (ransomNote, magazine) {
    var magazineMap = buildMapFromString(magazine)
    var ransomArr = ransomNote.split('')


    // use this variable to keep track of constructed string length
    var constructedStringLength = 0
    ransomArr.map((ransomChar) => {
        if (magazineMap[ransomChar]) {
            magazineMap[ransomChar] -= 1


            // when we reduce a number from the map, increment
            constructedStringLength += 1
        }
    })


    // if the final contructed length and ransom note length are same, its a match
    return constructedStringLength == ransomNote.length


};