1. Regular Expression Matching

Implement regular expression matching with support for'.'and'*'.

'.' Matches any single character.
'*' Matches zero or more of the preceding element.

public class Solution {

    public boolean isMatch(String s, String p) {

        int m = s.length();
        int n = p.length();
        boolean[][] dp = new boolean[m + 1][n + 1];

        dp[0][0] = true;

        for(int i = 1; i <= n; i ++) {
            if(p.charAt(i - 1) == '*')
                dp[0][i] = dp[0][i - 2];
        }

        for(int i = 1; i <= m; i ++) {
            for(int j = 1; j <= n; j ++) {

                if(s.charAt(i - 1) == p.charAt(j - 1) || p.charAt(j - 1) == '.')
                    dp[i][j] = dp[i - 1][j - 1];
                else if(p.charAt(j - 1) == '*') {

                    dp[i][j] = dp[i][j - 2];
                    if(s.charAt(i - 1) == p.charAt(j - 2) || p.charAt(j - 2) == '.')
                        dp[i][j] = dp[i][j] || dp[i - 1][j];
                }
            }
        }

        return dp[m][n];
    }
}

2. Wildcard Matching

Implement wildcard pattern matching with support for'?'and'*'.

'?' Matches any single character.
'*' Matches any sequence of characters (including the empty sequence, may contain different character).

public class Solution {
    public boolean isMatch(String s, String p) {

        int m = s.length();
        int n = p.length();

        boolean[][] dp = new boolean[m + 1][n + 1];
        dp[0][0] = true;

        for(int i = 1; i <= n; i ++) {
            dp[0][i] = (p.charAt(i - 1) == '*') && dp[0][i-1];
        }

        for(int i = 1; i <= m; i ++) {
            for(int j = 1; j <= n; j ++) {

                if(s.charAt(i - 1) == p.charAt(j - 1) || p.charAt(j - 1) == '?')
                    dp[i][j] = dp[i - 1][j - 1];
                else if(p.charAt(j - 1) == '*') {
                    dp[i][j] = dp[i][j - 1] || dp[i - 1][j];
                }
            }
        }

        return dp[m][n];
    }
}