Sword refers to Offer 16 (two-point thinking). The integer power of the value
Problem Description:
Implements pow( x , n ) , a function that computes x raised to the nth power (ie, xn). Library functions must not be used, and there is no need to consider large numbers.
Example:
输入：x = 2.00000, n = 10 输出：1024.00000
输入：x = 2.10000, n = 3 输出：9.26100
输入：x = 2.00000, n = -2 输出：0.25000
Code implementation (the idea is right, but the time limit is exceeded)
class Solution {
public double myPow(double x, int n) {
if(x == 0.0){
return 0.0;
}
if(n == 0){
return 1.0;
}
double number = 1.0;
if(n < 0){
x = 1/x;
n = -n;
}
while(n > 0){
number = number * x;
n -= 1;
}
return number;
}
}
Problem-solving ideas:Idea link
Code implementation: cut the time in half
class Solution {
public double myPow(double x, int n) {
if(x == 0.0){
return 0.0;
}
if(n == 0){
return 1.0;
}
double number = 1.0;
//将十进制n转化为二进制b
long b = n;
if(b < 0){
x = 1/x;
b = -b;
}
while(b > 0){
//当b为奇数时，额外乘以x
if((b & 1)== 1){
number *= x;
}
x *= x;
b >>= 1;
}
return number;
}
}