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Merge pull request TheAlgorithms#530 from rahul1995/binary-expo

Add Iterative Binary Exponentiation

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	`1`	`+// To calculate x^n i.e. exponent(x, n) in O(log n) time in iterative way`
	`2`	`+// n is an integer and n >= 0`
	`3`	`+`
	`4`	`+// Explanation: https://en.wikipedia.org/wiki/Exponentiation_by_squaring`
	`5`	`+`
	`6`	`+// Examples:`
	`7`	`+// 2^3 = 8`
	`8`	`+// 5^0 = 1`
	`9`	`+`
	`10`	`+// Uses the fact that`
	`11`	`+// exponent(x, n)`
	`12`	`+// = exponent(x*x, floor(n/2)) ; if n is odd`
	`13`	`+// = xexponent(xx, floor(n/2)) ; if n is even`
	`14`	`+const exponent = (x, n) => {`
	`15`	`+ let ans = 1`
	`16`	`+ while (n > 0) {`
	`17`	`+ if (n % 2 !== 0) ans *= x`
	`18`	`+ n = Math.floor(n / 2)`
	`19`	`+ if (n > 0) x *= x`
	`20`	`+ }`
	`21`	`+ return ans`
	`22`	`+}`
	`23`	`+`
	`24`	`+export { exponent }`

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	`1`	`+import { exponent } from '../BinaryExponentiationIterative'`
	`2`	`+`
	`3`	`+describe('exponent', () => {`
	`4`	`+ it('should return 1 when power is 0', () => {`
	`5`	`+ expect(exponent(5, 0)).toBe(1)`
	`6`	`+ })`
	`7`	`+`
	`8`	`+ it('should return 0 when base is 0', () => {`
	`9`	`+ expect(exponent(0, 7)).toBe(0)`
	`10`	`+ })`
	`11`	`+`
	`12`	`+ it('should return the value of a base raised to a power', () => {`
	`13`	`+ expect(exponent(3, 5)).toBe(243)`
	`14`	`+ })`
	`15`	`+})`

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