1.7 KiB
1.7 KiB
id | challengeType | title |
---|---|---|
5900f37d1000cf542c50fe8f | 5 | Problem 16: Power digit sum |
Description
exponent
?
Instructions
Tests
tests:
- text: <code>powerDigitSum(15)</code> should return 26.
testString: assert.strictEqual(powerDigitSum(15), 26, '<code>powerDigitSum(15)</code> should return 26.');
- text: <code>powerDigitSum(128)</code> should return 166.
testString: assert.strictEqual(powerDigitSum(128), 166, '<code>powerDigitSum(128)</code> should return 166.');
- text: <code>powerDigitSum(1000)</code> should return 1366.
testString: assert.strictEqual(powerDigitSum(1000), 1366, '<code>powerDigitSum(1000)</code> should return 1366.');
Challenge Seed
function powerDigitSum(exponent) {
// Good luck!
return true;
}
powerDigitSum(15);
Solution
function powerDigitSum(exponent) {
const bigNum = [1];
let sum = 0;
for (let i = 1; i <= exponent; i++) {
let count = bigNum.length + 1;
let overflow = 0;
for (let j = 0; j < count; j++) {
let digit = bigNum[j] || 0;
digit = 2 * digit + overflow;
if (digit > 9) {
digit -= 10;
overflow = 1;
} else {
overflow = 0;
}
bigNum[j] = digit;
}
}
bigNum.forEach(function(num) {
return sum += num;
});
return sum;
}