Hackerrank "Hash Tables: Ransom Note" Javascript Solution

Question

Here is the original problem, and here's my solution:

function main() {
 var m_temp = readLine().split(' ');
 var m = parseInt(m_temp[0]);
 var n = parseInt(m_temp[1]);
 magazine = readLine().split(' ');
 ransom = readLine().split(' ');
 var freqs = {}
 for (var i = 0; i < m; i++){
 freqs[magazine[i]] = (freqs[magazine[i]] || 0) + 1;
 }
 var result = "Yes"
 for (var j = 0; j < n; j++){
 if (freqs[ransom[j]] && freqs[ransom[j]] > 0){
 freqs[ransom[j]] -= 1;
 } else {
 result = "No"
 break;
 }
 }
 console.log(result)
}

I wonder if there's a more efficient solution than this? Thanks! I understand forEach could be used for code brevity, but I'm just using for loop for the extra performance benefit (https://coderwall.com/p/kvzbpa/don-t-use-array-foreach-use-for-instead)

• le_m: I expect this second for-loop body to execute a tiny bit faster: if (!--freqs[ransom[i]] >= 0){result = "No"; break;}
• kdenz: @le_m Nice! Your solutions seems to always be highly elegant.

Answer 1

Your solution may work for valid inputs, but you are not checking invalid input situations such as when the ransom letter contains more words than the ones in the magazine:

if(n > m):
 throw new Error("ransom can not be written from magazine");

You can even go further by checking if the first line corresponds to what it pretends to be:

if (magazine.length !== m) 
 throw new Error("Wrong words number in magazine");
if (ransom.length !== n) 
 throw new Error("Wrong words number in ransom");

You can refactor the above conditions in one single line:

if(n > m || agazine.length !== m || ransom.length !== n):
 throw new Error("Invalid input");

• kdenz: Right, edge cases! ty