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October 11, 2017 10:55
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Get "degree" of the string
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function getDegreeOfString(str, degree) { | |
let degreeOfStr = ""; | |
const errorMsg = "undefined"; | |
if (degree === 0) return ""; | |
if (degree === 1) return str; | |
if (degree > 1) { | |
for (let i = 0; i < (degree - 1); i++) { | |
degreeOfStr += str; | |
} | |
return degreeOfStr; | |
} | |
// например, "abcabc", degree = -2 | |
// "abcabc".length = 6 % 2 = 0 | |
// в противном случае, мы не сможем получить корень степени |degree| из str | |
if (str.length % (degree*(-1))) { | |
return errorMsg; | |
} | |
if (degree < 0) { | |
const length = str.length / (degree*(-1)); // размер искомой строки | |
let subStr = str.substring(0, length); // искомая строка | |
// проверяем заданную строку на вхождение одинаковых значений искомой строки | |
// str = subStr + subStr + ... + subStr | |
let index = length; | |
while (index < str.length) { | |
let nextSubStr = str.substring(index, index + length); | |
if (subStr !== nextSubStr) { | |
return errorMsg; | |
} | |
subStr = nextSubStr; | |
index += length; | |
} | |
return subStr; | |
} | |
} | |
console.info(getDegreeOfString("AbcdeAbcdeAbcde", -3)); // Abcde |
mikhail-dvorkin, actually you're right. Good point.
I changed a comment here a little bit:
"в противном случае, мы не сможем получить корень степени |degree| из str"
Thanks a lot for your feedback.
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Is is very unnatural to say that k-th root of a string is "power -k". The (~only) natural way would be to call it "power 1/k".
Because in current convention you have s^3 * s^-2 != s, which is very unwanted.