3
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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)

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  • 1
    \$\begingroup\$ I expect this second for-loop body to execute a tiny bit faster: if (!--freqs[ransom[i]] >= 0){result = "No"; break;} \$\endgroup\$ – le_m Jun 14 '17 at 17:54
  • \$\begingroup\$ @le_m Nice! Your solutions seems to always be highly elegant. \$\endgroup\$ – kdenz Jun 18 '17 at 15:25
1
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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");
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  • \$\begingroup\$ Right, edge cases! ty \$\endgroup\$ – kdenz Jun 18 '17 at 15:24

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