Chapter 4 exercise: fepona. Qi series & vampire numbers

Package COM. twoslow. cha4;/*** Fibonacci sequence: Starting from three numbers, each number is the sum of the first two: 1 1 2 3 5 8 13... * @ author sai **/public class Fibonacci {public static void main (string [] ARGs) {for (INT I = 0; I <10; I ++) {system. out. print (FIB (I) + ",") ;}} public static int fib (INT N) {If (n <2) return 1; return fib (n-1) + fib (n-2 );}}

Package COM. twoslow. cha4;/*** vampire number: a number with an even number, which can be multiplied by a number. * This number contains a half-digit number, the number * selected from the initial number can be sorted in any order. Numbers ending with two zeros are not allowed. * Eg: 1260 = 21*60; 1827 = 21*87; 2187 = 27*81 * Find all 4-digit vampire numbers. * @ Author sai **/public class vampirenumbers2 {static int A (int I) {// return I/1000;} static int B (int I) {// hundred bits return (I % 1000)/100;} static int C (int I) {// ten return (I % 1000) % 100)/10 ;} static int D (int I) {// return (I % 1000) % 100) % 10;} static int COM (int I, Int J) {return (I * 10) + J;} static void producttest (int I, int M, int N) {If (M * n = I) system. out. println (I + "=" + M + "*" + n);} public static void main (string [] ARGs) {long start = system. currenttimemillis (); For (INT I = 1001; I <9999; I ++) {// The permutation and combination of any number of 2 numbers from 4 is equal to 4 × 3 = 12 producttest (I, COM (a (I), B (I )), COM (C (I), D (I); producttest (I, COM (a (I), B (I), COM (d (I ), C (I); producttest (I, COM (a (I), C (I), COM (B (I), D (I ))); producttest (I, COM (a (I), C (I), COM (d (I), B (I); producttest (I, COM (a (I), D (I), COM (B (I), C (I); producttest (I, COM (a (I ), d (I), COM (C (I), B (I); producttest (I, COM (B (I), A (I )), COM (C (I), D (I); producttest (I, COM (B (I), A (I), COM (d (I ), C (I); producttest (I, COM (B (I), C (I), COM (d (I), A (I ))); producttest (I, COM (B (I), D (I), COM (C (I), A (I); producttest (I, COM (C (I), A (I), COM (d (I), B (I); producttest (I, COM (C (I ), B (I), COM (d (I), A (I);} long end = system. currenttimemillis (); system. out. println (end-Start); // simple test: The time is between 22 and 24, and 22 mostly }}

Package COM. twoslow. cha4; import Java. util. arrays;/*** vampire number: a number with an even number, which can be multiplied by a number. * This number contains a half-digit number, the number * selected from the initial number can be sorted in any order. Numbers ending with two zeros are not allowed. * Eg: 1260 = 21*60; 1827 = 21*87; 2187 = 27*81 * Find all 4-digit vampire numbers. * Result: 1260 = 21*60 1395 = 15*93 1435 = 41*35 1530 = 51*30 1827 = 87*21 2187 = 27*81 6880 = 86*80 6880 = 80*86 * @ author sai **/public class vampirenumbers3 {public static void main (string [] ARGs) {long start = system. currenttimemillis (); int I _val; char [] C1, C2; For (INT x = 10; x <100; X ++) {for (INT y = x + 1; Y <100; y ++) {I _val = x * Y; If (I _val % 100 = 0 & (I _val-x -Y) % 9! = 0) {continue;} C1 = string. valueof (I _val ). tochararray (); C2 = (string. valueof (x) + String. valueof (y )). tochararray (); arrays. sort (C1); arrays. sort (C2); If (arrays. equals (C1, C2) {system. out. println (I _val + "=" + x + "*" + Y) ;}} long end = system. currenttimemillis (); system. out. println (end-Start); // simple test: 31 32 mostly }}

Package COM. twoslow. cha4; import Java. util. arrays;/*** vampire number: a number with an even number, which can be multiplied by a number. * This number contains a half-digit number, the number * selected from the initial number can be sorted in any order. Numbers ending with two zeros are not allowed. * Eg: 1260 = 21*60; 1827 = 21*87; 2187 = 27*81 * Find all 4-digit vampire numbers. * Result: 1260 = 21*60 1395 = 15*93 1435 = 41*35 1530 = 51*30 1827 = 87*21 2187 = 27*81 6880 = 86*80 6880 = 80*86 * @ author sai **/public class vampirenumbers {public static void main (string [] ARGs) {long start = system. currenttimemillis (); string [] ar_str1, ar_str2; int sum = 0; int from; int to; int I _val; int COUNT = 0; // double loop for (INT I = 10; I <100; I ++) {// J = I + 1 to avoid repetition Not quite familiar with from &. If there are already 14 groups, from = math. max (1000/I, I + 1); To = math. min (10000/I, 100); For (Int J = from; j <to; j ++) {I _val = I * J; /** I _val % 100 = 0: exclude the ending number of 2 0 * I _val-i-j % 9! = 0: Any four digits can be considered as: I _val = 1000a + 100b + 10C + D * any two digits can be composed of any two of the four digits. For example, 10a + B, 10B + A, 10C + ..., we can see that the coefficient is 10 or 1 * I _val-I-j = 1000a + 100b + 10C + d-m1 * a-m2 * b-m3 * c-m4 * D * = (1000-m1) * A + (100-m2) * B + (10-m3) * C + (1-m4) * D * Whether M1, M2, M3, or M4 is 1 or 10, a, B, c, d. The coefficients of the four numbers are multiples of 9. * **/If (I _val % 100 = 0 | (I _val-I-j) % 9! = 0) {continue;} count ++; ar_str1 = string. valueof (I _val ). split (""); // If I _val = "1260", ar_str1 = {"", "1", "2", "6 ", "0"} ar_str2 = (string. valueof (I) + String. valueof (j )). split (""); arrays. sort (ar_str1); arrays. sort (ar_str2);/** sort to determine whether all four numbers are the same */If (arrays. equals (ar_str1, ar_str2) {// compare after sorting. If it is true, a set of sum ++; system is found. out. println ("Number" + sum + "group:" + I + "*" + J + "=" + I _val) ;}} long end = system. currenttimemillis (); system. out. println (end-Start); system. out. println ("found" + sum + "Number of vampire groups"); system. out. println (count); // simple test: the time range is 17-20, 18 and 19 }}