LintCode 154. Regular Expression Matching

http://www.lintcode.com/en/problem/regular-expression-matching/



A classic Google Problem.

A classic matching dp.

the Dynamic Programming Elements:

1. state
dp i, j means first i of A matching with first j of B.

2. Init
dp i, 0 -> i == 0;
dp 0, j -> isEmpty(j)

3. Func
dp i, j =
if(B.chatAt(j) == '*') {
  check if the Ai matches, then |= helper(i - 1, j)
  and always we can do without Bj, so |= helper(i, j - 2)
} else {
  Bj match Ai? then |= helper(i - 1, j - 1);
  else false;
}

4. Answer
dp m, n

PS: dp size m + 1 by n + 1.