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	`1`	`+# 50. Pow(x, n)`
	`2`	`+实现 pow(x, n) ,即计算 x 的 n 次幂函数。`
	`3`	`+`
	`4`	+难度: `middle`
	`5`	`+`
	`6`	`+## 示例`
	`7`	`+`
	`8`	+```
	`9`	`+示例 1:`
	`10`	`+`
	`11`	`+输入: 2.00000, 10`
	`12`	`+输出: 1024.00000`
	`13`	`+示例 2:`
	`14`	`+`
	`15`	`+输入: 2.10000, 3`
	`16`	`+输出: 9.26100`
	`17`	+```
	`18`	`+`
	`19`	`+## 解题思路`
	`20`	`+`
	`21`	`+分治法,「快速幂算法」的本质是分治算法。举个例子,如果我们要计算x^64次幂 ,我们可以按照:`
	`22`	`+`
	`23`	`+x -> x^2 -> x^4 -> x^8 -> x^{16} -> x^{32} -> x^{64}`
	`24`	`+`
	`25`	`+分治的核心是递归,代码如下:`
	`26`	`+`
	`27`	+```javascript
	`28`	`+/**`
	`29`	`+ * @param {number} x`
	`30`	`+ * @param {number} n`
	`31`	`+ * @return {number}`
	`32`	`+ */`
	`33`	`+var myPow = function(x, n) {`
	`34`	`+ return n > 0 ? quickMul(x, n) : 1.0 / quickMul(x, -n);`
	`35`	`+};`
	`36`	`+`
	`37`	`+var quickMul = function(x, N) {`
	`38`	`+ if (N == 0) {`
	`39`	`+ return 1.0`
	`40`	`+ }`
	`41`	`+ let y = quickMul(x, Math.floor(N / 2));`
	`42`	`+ return N % 2 == 0 ? y * y : y * y * x;`
	`43`	`+}`
	`44`	+```

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