8.23 - hard - 94

488. Zuma Game

对每一个s消除三个连续的球，然后对于每一个可以消除的位置进行搜索，取其最小值。这道题的解法和思路比较复杂，但是也比较清晰，值得再写一遍。

class Solution(object):
    def findMinStep(self, board, hand):
        """
        :type board: str
        :type hand: str
        :rtype: int
        """
        self.MAXCOUNT = 6
        handCount = [0] * 26
        for c in hand:
            handCount[ord(c) - ord('A')] += 1
        res = self.helper(board + "#", handCount);  #append a "#" to avoid special process while j==board.length, make the code shorter.
        return -1 if res == self.MAXCOUNT else res
        
    def helper(self, s, h):
        s = self.removeConsecutive(s)   
        if s == "#":
            return 0
        res = self.MAXCOUNT
        need = 0
        i = 0
        for j in range(len(s)):
            if s[i] == s[j]:
                continue
            need = 3 - (j - i)     #balls need to remove current consecutive balls.
            if h[ord(s[i]) - ord('A')] >= need:
                h[ord(s[i]) - ord('A')] -= need
                res = min(res, need + self.helper(s[0:i] + s[j:], h))
                h[ord(s[i]) - ord('A')] += need
            i = j
        return res
    
    #remove consecutive balls longer than 3
    def removeConsecutive(self, board):
        i = 0
        for j in range(len(board)):
            if board[i] == board[j]:
                continue
            if j - i >= 3:
                return self.removeConsecutive(board[0:i] + board[j:])
            else:
                i = j
        return board