'.' Matches any single character.
'*' Matches zero or more of the preceding element.The matching should cover the entire input string (not partial).The function prototype should be:
bool isMatch(const char *s, const char *p)Some examples:
isMatch("aa","a") → false
isMatch("aa","aa") → true
isMatch("aaa","aa") → false
isMatch("aa", "a*") → true
isMatch("aa", ".*") → true
isMatch("ab", ".*") → true
isMatch("aab", "c*a*b") → true

1, If p.charAt(j) == s.charAt(i) :  dp[i][j] = dp[i-1][j-1];
2, If p.charAt(j) == '.' : dp[i][j] = dp[i-1][j-1];
3, If p.charAt(j) == '*': here are two sub conditions:1   if p.charAt(j-1) != s.charAt(i) : dp[i][j] = dp[i][j-2]  //in this case, a* only counts as empty2   if p.charAt(i-1) == s.charAt(i) or p.charAt(i-1) == '.':dp[i][j] = dp[i-1][j]    //in this case, a* counts as multiple a or dp[i][j] = dp[i][j-1]   // in this case, a* counts as single aor dp[i][j] = dp[i][j-2]   // in this case, a* counts as empty

package T010;public class RegularExpressionMatching {public static void main(String[] args) {System.out.println(isMatch("aab","c*a*b"));}public static boolean isMatch(String s, String p) {if (s == null || p == null) {return false;}boolean[][] dp = new boolean[s.length()+1][p.length()+1];dp[0][0] = true;for (int i = 0; i < p.length(); i++) {if (p.charAt(i) == '*' && dp[0][i-1]) {dp[0][i+1] = true;}}printArray(dp);for (int i = 0 ; i < s.length(); i++) {for (int j = 0; j < p.length(); j++) {if (p.charAt(j) == '.' || 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] || dp[i][j+1] || dp[i+1][j-1]);}}}}// printArray(dp);return dp[s.length()][p.length()];}/* * isMatch("aa","a") → false* isMatch("aa","aa") → true* isMatch("aaa","aa") → false* isMatch("aa", "a*") → true* isMatch("aa", ".*") → true* isMatch("ab", ".*") → true* isMatch("aab", "c*a*b") → true*/public static void printArray(boolean [] arr){System.out.print("printArray:");for(int i=0;i<arr.length;i++){System.out.print(arr[i]+" ");}System.out.println("");}public static void printArray(boolean[][] V){System.out.println("printArray:");int rows = V.length;int cols = V[0].length;for(int i=0;i<rows;i++){for(int j=0;j<cols;j++){System.out.print(V[i][j]+" ");}System.out.println("");}System.out.println("");}
}