5.7 KiB
5.7 KiB
title | id | challengeType |
---|---|---|
24 game | 5951e88f64ebf159166a1176 | 5 |
Description
Instructions
Rules:
- Only the following operators/functions are allowed: multiplication, division, addition, subtraction.
- Division should use floating point or rational arithmetic, etc, to preserve remainders.
- Forming multiple digit numbers from the supplied digits is disallowed. (So an answer of 12+12 when given 1, 2, 2, and 1 is wrong).
- The order of the digits when given does not have to be preserved.
Example input | Example output |
---|---|
solve24("4878"); |
(7-8/8)*4 |
solve24("1234"); |
314*2 |
solve24("6789"); |
(6*8)/(9-7) |
solve24("1127"); |
(1+7)*(2+1) |
Tests
tests:
- text: <code>solve24</code> is a function.
testString: assert(typeof solve24 === 'function', '<code>solve24</code> is a function.');
- text: <code>solve24("4878")</code> should return <code>(7-8/8)*4</code> or <code>4*(7-8/8)</code>
testString: assert(include(answers[0], solve24(testCases[0])), '<code>solve24("4878")</code> should return <code>(7-8/8)*4</code> or <code>4*(7-8/8)</code>');
- text: <code>solve24("1234")</code> should return any arrangement of <code>1*2*3*4</code>
testString: assert(include(answers[1], solve24(testCases[1])), '<code>solve24("1234")</code> should return any arrangement of <code>1*2*3*4</code>');
- text: <code>solve24("6789")</code> should return <code>(6*8)/(9-7)</code> or <code>(8*6)/(9-7)</code>
testString: assert(include(answers[2], solve24(testCases[2])), '<code>solve24("6789")</code> should return <code>(6*8)/(9-7)</code> or <code>(8*6)/(9-7)</code>');
- text: <code>solve24("1127")</code> should return a permutation of <code>(1+7)*(1*2)</code>
testString: assert(include(answers[3], solve24(testCases[3])), '<code>solve24("1127")</code> should return a permutation of <code>(1+7)*(1*2)</code>');
Challenge Seed
function solve24 (numStr) {
// Good luck!
return true;
}
After Test
const testCases = [
'4878',
'1234',
'6789',
'1127'
];
const answers = [
['(7-8/8)*4', '4*(7-8/8)', '(4-8+7)*8', '(4+7-8)*8', '(7+4-8)*8', '(7-8+4)*8', '8*(4-8+7)', '8*(4+7-8)', '8*(7+4-8)', '8*(7-8+4)'],
['1*2*3*4', '1*2*4*3', '1*3*2*4', '1*3*4*2', '1*4*2*3', '1*4*3*2', '2*1*3*4', '2*1*4*3', '2*3*1*4', '2*3*4*1', '2*4*3*1', '2*4*1*3', '3*1*2*4', '3*1*4*2', '3*2*1*4', '3*2*4*1', '3*4*1*2', '3*4*2*1', '4*1*2*3', '4*1*3*2', '4*2*1*3', '4*2*3*1', '4*3*1*2', '4*3*2*1', '(1+2+3)*4', '(1+3+2)*4', '(2+1+3)*4', '(2+3+1)*4', '(3+1+2)*4', '(3+2+1)*4', '4*(1+2+3)', '4*(2+1+3)', '4*(2+3+1)', '4*(3+1+2)', '4*(3+2+1)'],
['(6*8)/(9-7)', '(8*6)/(9-7)', '6*8/(9-7)', '8*6/(9-7)'],
['(1+7)*(2+1)', '(1+7)*(1+2)', '(1+2)*(1+7)', '(1+2)*(7+1)', '(2+1)*(1+7)', '(7+1)*(2+1)']
];
function include(ansArr, res) {
const index = ansArr.indexOf(res);
return index >= 0;
}
Solution
// noprotect
function solve24(numStr) {
const digitsArr = numStr.split('');
const answers = [];
const digitPermutations = [];
const operatorPermutations = [];
function generateDigitPermutations (digits, permutations = []) {
if (digits.length === 0) {
digitPermutations.push(permutations);
}
else {
for (let i = 0; i < digits.length; i++) {
const curr = digits.slice();
const next = curr.splice(i, 1);
generateDigitPermutations(curr.slice(), permutations.concat(next));
}
}
}
function generateOperatorPermutations (permutations = []) {
const operators = ['+', '-', '*', '/'];
if (permutations.length === 3) {
operatorPermutations.push(permutations);
}
else {
for (let i = 0; i < operators.length; i++) {
const curr = permutations.slice();
curr.push(operators[i]);
generateOperatorPermutations(curr);
}
}
}
generateDigitPermutations(digitsArr);
generateOperatorPermutations();
interleave();
return answers[0];
function interleave () {
for (let i = 0; i < digitPermutations.length; i++) {
for (let j = 0; j < operatorPermutations.length; j++) {
const d = digitPermutations[i];
const o = operatorPermutations[j];
const perm = [
`${d[0]}${o[0]}${d[1]}${o[1]}${d[2]}${o[2]}${d[3]}`,
`(${d[0]}${o[0]}${d[1]})${o[1]}${d[2]}${o[2]}${d[3]}`,
`${d[0]}${o[0]}(${d[1]}${o[1]}${d[2]})${o[2]}${d[3]}`,
`${d[0]}${o[0]}${d[1]}${o[1]}(${d[2]}${o[2]}${d[3]})`,
`${d[0]}${o[0]}(${d[1]}${o[1]}${d[2]}${o[2]}${d[3]})`,
`(${d[0]}${o[0]}${d[1]}${o[1]}${d[2]})${o[2]}${d[3]}`,
`(${d[0]}${o[0]}${d[1]})${o[1]}(${d[2]}${o[2]}${d[3]})`
];
perm.forEach(combination => {
const res = eval(combination);
if (res === 24) {
return answers.push(combination);
}
});
}
}
}
}