GeezerVison is showing github.com — Created Problem04 in project_euler · JavaInCloud/Java@623210b
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Copy file name to clipboard +41Lines changed: 41 additions & 0 deletions | Original file line number | Diff line number | Diff line change |
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| 1 | +package ProjectEuler; |
| 2 | + |
| 3 | +/** |
| 4 | + * A palindromic number reads the same both ways. |
| 5 | + * The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99. |
| 6 | + * <p> |
| 7 | + * Find the largest palindrome made from the product of two 3-digit numbers. |
| 8 | + * <p> |
| 9 | + * link: https://projecteuler.net/problem=4 |
| 10 | + */ |
| 11 | +public class Problem04 { |
| 12 | + public static void main(String[] args) { |
| 13 | + |
| 14 | + assert solution1(10000) == -1; |
| 15 | + assert solution1(20000) == 19591; /* 19591 == 143*137 */ |
| 16 | + assert solution1(30000) == 29992; /* 29992 == 184*163 */ |
| 17 | + assert solution1(40000) == 39893; /* 39893 == 287*139 */ |
| 18 | + assert solution1(50000) == 49894; /* 49894 == 494*101 */ |
| 19 | + assert solution1(60000) == 59995; /* 59995 == 355*169 */ |
| 20 | + assert solution1(70000) == 69996; /* 69996 == 614*114 */ |
| 21 | + assert solution1(80000) == 79897; /* 79897 == 733*109 */ |
| 22 | + assert solution1(90000) == 89798; /* 89798 == 761*118 */ |
| 23 | + assert solution1(100000) == 99999; /* 100000 == 813*123 */ |
| 24 | + } |
| 25 | + |
| 26 | + private static int solution1(int n) { |
| 27 | + for (int i = n - 1; i >= 10000; --i) { |
| 28 | + String strNumber = String.valueOf(i); |
| 29 | + |
| 30 | + /* Test if strNumber is palindrome */ |
| 31 | + if (new StringBuilder(strNumber).reverse().toString().equals(strNumber)) { |
| 32 | + for (int divisor = 999; divisor >= 100; --divisor) { |
| 33 | + if (i % divisor == 0 && String.valueOf(i / divisor).length() == 3) { |
| 34 | + return i; |
| 35 | + } |
| 36 | + } |
| 37 | + } |
| 38 | + } |
| 39 | + return -1; /* not found */ |
| 40 | + } |
| 41 | +} |