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Pow.java
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27 lines (25 loc) · 630 Bytes
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public class Pow {
/**
* 这道题要注意的有几点：
* 1. n为0的情况
* 2. n为负数的情况，要给n变为正，同时x取倒
* 3. n由负变正可能会溢出，所以要改成long
*/
public double myPow(double x, int n) {
return helper(x, n);
}
private double helper(double x, long n) {
if (n == 0) {
return 1;
}
if (n < 0) {
return helper(1 / x, -n);
}
double y = helper(x, n / 2);
if (n % 2 == 0) {
return y * y;
} else {
return y * y * x;
}
}
}