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24 lines
558 B
JavaScript
24 lines
558 B
JavaScript
// To calculate x^n i.e. exponent(x, n) in O(log n) time in iterative way
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// n is an integer and n >= 0
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// Explanation: https://en.wikipedia.org/wiki/Exponentiation_by_squaring
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// Examples:
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// 2^3 = 8
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// 5^0 = 1
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// Uses the fact that
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// exponent(x, n)
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// = exponent(x*x, floor(n/2)) ; if n is odd
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// = x*exponent(x*x, floor(n/2)) ; if n is even
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const exponent = (x, n) => {
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let ans = 1
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while(n > 0) {
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if(n%2 != 0) ans *= x
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n = Math.floor(n/2)
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if(n > 0) x *= x
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}
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return ans
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}
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export { exponent } |