水仙花数

仙花数是指一个 n 位数 ( n≥3 )，它的每个位上的数字的 n 次幂之和等于它本身。

 

import java.util.Date;public class ArmstrongNumber {public static long[] BIT_NUMBERS = new long[23];static {for(int i = 0; i < 10; i ++){BIT_NUMBERS[i] = calCBit(10, i-1);}}/** * 计算次方 * */public static long calc(int cnum){long numbers = 1;for(int i = 0; i < cnum; i ++){numbers *= 9;}return numbers;}/** * @param args */public static void main(String[] args) {//System.out.println(isTrue(153,(byte)3));//System.out.println(Long.bitCount(23));//System.out.println(isTrue(4234,(byte)calBit(153)));Date dateBegin = new Date();for(long i = 101; i < 100000000l; i ++){if(isTrue(i,(byte)calBit(i))){//System.out.println(i);}}Date dateEnd = new Date();System.out.println(dateBegin + " " + dateEnd);}/** * 判断一个数是否是水仙花数 * */private static boolean isTrue(int number){String numstr = String.valueOf(number);int length = numstr.length();int number0 = 0;for(int i = 0; i < length; i ++){//计算次方int b3bit = (int)Math.pow(Byte.parseByte(numstr.charAt(i)+""), length);number0 += b3bit;}//是否相等if(number == number0){return true;}else{return false;}}/** * 法二 * */private static boolean isTrue(long number,byte bit){long sum = 0;long number0 = number;for(int i = 0; i < bit; i ++){//取位数字//从最高位开始取int numbit = 0;if(number0 > 10){long num = BIT_NUMBERS[bit-i];//calCBit(10,bit-i-1);numbit = (int)(number0/num);number0 = number0 - num * numbit;}else{numbit = (int)number0;}//计算该位的次方sum += calCBit(numbit,bit);}if(sum == number){return true;}else{return false;}}/** * 计算次方 * */private static long calCBit(int num,int bit){long temp = 1;for(int i =0; i < bit; i ++){temp *= num;}return temp;}private static int calBit(long num){for(int i = 3; i < 20; i ++){int bnum = (int)(num / BIT_NUMBERS[i]);if(bnum > 0 && bnum < 10){return i;}}return 0;}}