Find maximum possible time HH:MM by permuting four given digits

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 23  2060

执念已碎 2020-11-30 02:44

I recently took a coding test for a promotion at work. This was one of the tasks I really struggled with and was wondering what is the best way to do this. I used a load of

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离开以前 (楼主)

2020-11-30 02:59

The idea:

Find all combinations array (24 total)
filter out all invalid combinations (time format)
find the time value
output the array with the max time value

Solution:

First allCom will return all combination of the 4 number (total 24 combinations)

Then for the 24 array (combinations) call .forEach go through each array check if it is a valid time format. If it is valid time format then calculate the time value with

If the time is AB:CD then the value:

A = A * 10 hours = A * 10 * 3600s = A * 36000s

B = B * 1 hour = B * 3600s

C = C * 10s

D = D

Total value = A*36000 + B*3600 + C*10 + D

Now you got the value of the current array, compare with the saved Max, replace the max if this value is bigger.

At the end of the loop determine if a max found or it is not valid.

generate(6, 5, 2, 0);
generate(3, 9, 5, 0);
generate(7, 6, 3, 8);
generate(1, 7, 2, 7);
generate(1, 1, 1, 2);

// return all combination of 4 number (24 combination total)
function allCom(inputArray) {
  var result = inputArray.reduce(function permute(res, item, key, arr) {
    return res.concat(arr.length > 1 && arr.slice(0, key).concat(arr.slice(key + 1)).reduce(permute, []).map(function(perm) {
      return [item].concat(perm);
    }) || item);
  }, []);
  return result;
}

// core function to determine the max comb
function generate(A, B, C, D) {
  let input = [A, B, C, D];
  let allComb = allCom(input);
  let max = '';
  let maxA = [];

  allComb.forEach(function(comb, index, arr) {
    if (validCom(comb)) {
      let temp = calValue(comb);
      maxA = temp > max ? comb : maxA;
      max = temp > max ? temp : max;
    }
    if (index == allComb.length - 1) {
      if (max) {
        return console.log('For ' + JSON.stringify(input) + ' found max comb: ' + maxA[0] + maxA[1] + ':' + maxA[2] + maxA[3]);
      }
      return console.log('Sorry ' + JSON.stringify(input) + ' is not valid');
    }
  });
}

// check if this array is valid time format, ex [1,2,9,0] false, [2,2,5,5] true
function validCom(ar) {
  if (ar[0] <= 2 && ((ar[0] == 2 && ar[1] < 4) || (ar[0] != 2 && ar[1] <= 9)) && ar[2] <= 5 && ar[3] <= 9) {
    return true;
  }
  return false;
}

// calculate the total value of this comb array
function calValue(ar) {
  return +ar[0] * 36000 + +ar[1] * 3600 + +ar[2] * 10 + +ar[0];
}


$('button').on('click', function(e) {
    let inp = $('select');
    generate(inp[0].value, inp[1].value, inp[2].value, inp[3].value);
});


var s = $('


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