RegularExpressionMatching2.java

/**
 * Created by cpacm on 2017/1/13.
 */
public class RegularExpressionMatching2 {

    public static void main(String[] args) {
        System.out.println(isMatch("agfsaasd", "azxcv.*"));
    }

    public static boolean isMatch(String s, String p) {
        if (s == null || p == null) {
            return false;
        }
        int m = s.length();
        int n = p.length();
        boolean[][] dp = new boolean[m + 1][n + 1];
        dp[0][0] = true;
        for (int j = 0; j < n; j++) {
            if (p.charAt(j) == '*') {
                dp[0][j + 1] = dp[0][j - 1];
            }
        }
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (p.charAt(j) == '.') {
                    dp[i + 1][j + 1] = dp[i][j];
                }
                if (p.charAt(j) == s.charAt(i)) {
                    dp[i + 1][j + 1] = dp[i][j];
                }
                if (p.charAt(j) == '*') {
                    if (p.charAt(j - 1) != s.charAt(i) && p.charAt(j - 1) != '.') {
                        dp[i + 1][j + 1] = dp[i + 1][j - 1];
                    } else {
                        dp[i + 1][j + 1] = dp[i + 1][j - 1] || dp[i + 1][j] || dp[i][j + 1];
                    }
                }
            }
        }
        return dp[m][n];
    }
}