10 - Regular Expression Matching

 JAVA

• class Solution {
      public boolean isMatch(String s, String p) {
          int m = s.length(), n = p.length();
          boolean[][] f = new boolean[m + 1][n + 1];
          f[0][0] = true;
          for (int i = 0; i <= m; ++i) {
              for (int j = 1; j <= n; ++j) {
                  if (p.charAt(j - 1) == '*') {
                      f[i][j] = f[i][j - 2];
                      if (i > 0 && (p.charAt(j - 2) == '.' || p.charAt(j - 2) == s.charAt(i - 1))) {
                          f[i][j] |= f[i - 1][j];
                      }
                  } else if (i > 0
                      && (p.charAt(j - 1) == '.' || p.charAt(j - 1) == s.charAt(i - 1))) {
                      f[i][j] = f[i - 1][j - 1];
                  }
              }
          }
          return f[m][n];
      }
  }

C++

• class Solution {
  public:
      bool isMatch(string s, string p) {
          int m = s.size(), n = p.size();
          bool f[m + 1][n + 1];
          memset(f, false, sizeof f);
          f[0][0] = true;
          for (int i = 0; i <= m; ++i) {
              for (int j = 1; j <= n; ++j) {
                  if (p[j - 1] == '*') {
                      f[i][j] = f[i][j - 2];
                      if (i && (p[j - 2] == '.' || p[j - 2] == s[i - 1])) {
                          f[i][j] |= f[i - 1][j];
                      }
                  } else if (i && (p[j - 1] == '.' || p[j - 1] == s[i - 1])) {
                      f[i][j] = f[i - 1][j - 1];
                  }
              }
          }
          return f[m][n];
      }
  };