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【JAVA大數訓練】Exponentiation
Exponentiation
Time Limit: 1000/500 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 6571 Accepted Submission(s): 1824
Problem Description
Problems involving the computation of exact values of very large magnitude and precision are common. For example, the
computation of the national debt is a taxing experience for many computer systems.
This problem requires that you write a program to compute the exact value of Rn where R is a real number ( 0.0 < R < 99.999 )
and n is an integer such that 0 < n <= 25.
Input
The input will consist of a set of pairs of values for R and n. The R value will occupy columns 1 through 6, and the n value
will be in columns 8 and 9.
Output
The output will consist of one line for each line of input giving the exact value of R^n. Leading zeros should be suppressed
in the output. Insignificant trailing zeros must not be printed. Don't print the decimal point if the result is an integer.
Sample Input
95.123 12
0.4321 20
5.1234 15
6.7592 9
98.999 10
1.0100 12
Sample Output
548815620517731830194541.899025343415715973535967221869852721
.00000005148554641076956121994511276767154838481760200726351203835429763013462401
43992025569.928573701266488041146654993318703707511666295476720493953024
29448126.764121021618164430206909037173276672
90429072743629540498.107596019456651774561044010001
1.126825030131969720661201
Source
East Central North America 1988
import java.math.BigDecimal;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input=new Scanner(System.in);
while(input.hasNext())
{
BigDecimal n=input.nextBigDecimal();
int m=input.nextInt();
n=n.pow(m);
String str=n.stripTrailingZeros().toPlainString();
if(str.charAt(0)=='0') //如果開頭為0，將0去掉（如0.2隻輸出.2）
System.out.println(str.substring(1));
else
System.out.println(str);
}
}
}
總結：
1.charAt(int index)方法
是一個能夠用來檢索特定索引下的字符的String實例的方法。
charAt()方法返回一個位於提供給它的參數索引處的字符。
s.chatAt(i)的意義就是，i為條件，就是第幾個字符，i的取值範圍為小於s的長度.
2.substring(參數)是java中截取字符串的一個方法有兩種傳參方式一種是public String substring(int beginIndex)返回一個新的字符串，
它是此字符串的一個子字符串。該子字符串從指定索引處的字符開始，直到此字符串末尾。另一種是public String substring(int
beginIndex, int endIndex)返回一個新字符串，它是此字符串的一個子字符串。該子字符串從指定的 beginIndex 處開始，直到索引
endIndex - 1 處的字符。因此，該子字符串的長度為 endIndex-beginIndex。
最後更新：2017-04-03 12:56:11