如何使用Java计算次方
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共2个回答
热心网友
计算2的N次方
时间*: 1000ms内存*: 65536kB
描述
任意给定一个正整数N(N<=100)，计算2的N次方的值。
输入
输入只有一个正整数N。
输出
输出2的N次方的值。
样例输入
5
样例输出
32
参考代码
[java] view plain copy print?
import java.util.*;
public class Main {
public final static int SIZE = 30;
public static void main(String[] args) throws Exception {
Scanner cin = new Scanner(System.in);
int n = cin.nextInt();
int res[] = new int[SIZE + 1];
int i;
for(i = 0;i < SIZE;++ i){
res[i] = 0;
}
res[0] = 1;
while(n > 0){
for(i = 0;i < SIZE;++ i){
res[i] *= 2;
}
for(i = 0;i < SIZE;++ i){
if(res[i] > 9){
res[i + 1] += res[i] / 10;
res[i] %= 10;
}
}
n --;
}
boolean bl = false;
StringBuffer bf = new StringBuffer();
for(i = SIZE;i >= 0;-- i){
if(res[i] != 0 || bl){
bf.append(res[i]);
bl = true;
}
}
System.out.println(bf);
}
}
根据高位低位改进的代码:
[java] view plain copy print?
/*
* Title :power 2
* From :http://blog.csdn.net/binfeihan/article/details/6858655
* Time :2011-10-11 21:10PM
* Author :Eric Zhou,binfeihan
* Email :binfeihan@126.com
*/
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Main {
public static void main(String[] args) throws IOException{
BufferedReader cin = new BufferedReader(new InputStreamReader(System.in));
int n = Integer.parseInt(cin.readLine().trim());
System.out.println(my_power_2(n));
//System.out.println(Long.MAX_VALUE);
//System.out.println(Long.MIN_VALUE);
}
public static StringBuffer my_power_2(int N){
StringBuffer v = new StringBuffer("");
long num[] = new long[2];
num[1] = 1;
if(N > 62){
num[0] = 1;
num[0] = num[0]<<(N - 62);
num[1] = num[1]<<62;
String s = String.valueOf(num[1]);
int size = 30,i = 0,j = 0;
long n[] = new long[size + 1];
//System.out.println(num[0]+" "+s);
for(i = s.length() - 1;i >= 0;-- i){
n[j ++] = (long) (num[0] * (s.charAt(i) - '0'));
//System.out.println(n[j - 1]);
}
for(i = 0;i < size;++ i){
while(n[i] > 9){
n[i + 1] += n[i] / 10;
n[i] %= 10;
}
}
boolean bl = false;
for(i = size;i >= 0;-- i){
if(n[i] != 0 || bl){
v.append(n[i]);
bl = true;
}
}
}else{
num[1] = num[1] << N;
v.append(String.valueOf(num[1]));
}
return v;
}
}
热心网友
Math.pow(a, b),
参数a是底数，参数b是多少次方，
如Math.pow(10, 2)=100,10的2次方
