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| 1 | +using System; |
| 2 | +using System.Text; |
| 3 | + |
| 4 | +public class Solution |
| 5 | +{ |
| 6 | + #region Brute Force |
| 7 | + private static bool _IsPalindrome(string s) |
| 8 | + { |
| 9 | + if (string.IsNullOrWhiteSpace(s)) |
| 10 | + { |
| 11 | + return false; |
| 12 | + } |
| 13 | + |
| 14 | + if (s.Length == 1) |
| 15 | + { |
| 16 | + return true; |
| 17 | + } |
| 18 | + |
| 19 | + for (int i = 0; i <= s.Length / 2; i++) |
| 20 | + { |
| 21 | + if (s[i] != s[s.Length - i - 1]) |
| 22 | + { |
| 23 | + return false; |
| 24 | + } |
| 25 | + } |
| 26 | + |
| 27 | + return true; |
| 28 | + } |
| 29 | + public static int CountSubstrings(string s) |
| 30 | + { |
| 31 | + if (string.IsNullOrWhiteSpace(s)) |
| 32 | + { |
| 33 | + return 0; |
| 34 | + } |
| 35 | + |
| 36 | + int count = s.Length; |
| 37 | + StringBuilder sb = new StringBuilder(); |
| 38 | + |
| 39 | + for (int i = 0; i < s.Length; i++) |
| 40 | + { |
| 41 | + sb.Clear(); |
| 42 | + sb.Append(s[i]); |
| 43 | + |
| 44 | + for (int j = i + 1; j < s.Length; j++) |
| 45 | + { |
| 46 | + sb.Append(s[j]); |
| 47 | + if (_IsPalindrome(sb.ToString())) |
| 48 | + { |
| 49 | + count++; |
| 50 | + } |
| 51 | + } |
| 52 | + } |
| 53 | + |
| 54 | + return count; |
| 55 | + } |
| 56 | + #endregion |
| 57 | + |
| 58 | + #region Two-Pointers |
| 59 | + private static int _CountPalindrome(string s, int left, int right) |
| 60 | + { |
| 61 | + int count = 0; |
| 62 | + while (left >= 0 && right < s.Length && s[left] == s[right]) |
| 63 | + { |
| 64 | + count++; |
| 65 | + |
| 66 | + left--; |
| 67 | + right++; |
| 68 | + } |
| 69 | + |
| 70 | + return count; |
| 71 | + } |
| 72 | + public static int CountSubstrings2(string s) |
| 73 | + { |
| 74 | + if (string.IsNullOrWhiteSpace(s)) |
| 75 | + { |
| 76 | + return 0; |
| 77 | + } |
| 78 | + |
| 79 | + int count = 0; |
| 80 | + |
| 81 | + for (int i = 0; i < s.Length; i++) |
| 82 | + { |
| 83 | + // Odd Length Palindrome |
| 84 | + count += _CountPalindrome(s, i, i); |
| 85 | + |
| 86 | + // Even Length Palindrome |
| 87 | + count += _CountPalindrome(s, i, i + 1); |
| 88 | + } |
| 89 | + |
| 90 | + return count; |
| 91 | + } |
| 92 | + #endregion |
| 93 | + |
| 94 | + public static void Main(string[] args) |
| 95 | + { |
| 96 | + Console.WriteLine(CountSubstrings("abaaba")); |
| 97 | + Console.WriteLine(CountSubstrings2("abaaba")); |
| 98 | + |
| 99 | + Console.ReadKey(); |
| 100 | + } |
| 101 | +} |
| 102 | + |
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