Java练习题-求1000!的结果中包含多少个0

import java.math.BigDecimal;

/**
* 求1000！的结果中包含多少个0？注：1000! = 1×2×3×4×5×…×999×1000
* @author Tang
*
*/
public class Test9 {

private static final BigDecimal oneBigDecimal=new BigDecimal(1);

/**
 * 计算'0'在字符串中的个数
 * @param str
 * @return
 */
public static int getZeroCount(String str){
    int count=0;
    for (int i = 0; i < str.length(); i++) {
        if(str.charAt(i)=='0'){
            count++;
        }
    }
    return count;
}

/**
 * 计算阶乘
 * @param number
 * @return
 */
private static BigDecimal computeFactorial(BigDecimal number){
    if (number.compareTo(oneBigDecimal)<=0) {
        return oneBigDecimal;
    }
    return number.multiply(computeFactorial(number.subtract(oneBigDecimal)));
}

public static void main(String[] args) {
    BigDecimal result = computeFactorial(new BigDecimal(1000));
    System.out.println(result);
    System.out.println(getZeroCount(result.toString()));
}

}

转载于:https://my.oschina.net/tangzhichao/blog/781399