488. Zuma Game

Think about Zuma Game. You have a row of balls on the table, colored red(R), yellow(Y), blue(B), green(G), and white(W). You also have several balls in your hand.

Each time, you may choose a ball in your hand, and insert it into the row (including the leftmost place and rightmost place). Then, if there is a group of 3 or more balls in the same color touching, remove these balls. Keep doing this until no more balls can be removed.

Find the minimal balls you have to insert to remove all the balls on the table. If you cannot remove all the balls, output -1.

 

Examples:
Input: "WRRBBW", "RB" Output: -1 Explanation: WRRBBW -> WRR[R]BBW -> WBBW -> WBB[B]W -> WW Input: "WWRRBBWW", "WRBRW" Output: 2 Explanation: WWRRBBWW -> WWRR[R]BBWW -> WWBBWW -> WWBB[B]WW -> WWWW -> empty Input:"G", "GGGGG" Output: 2 Explanation: G -> G[G] -> GG[G] -> empty Input: "RBYYBBRRB", "YRBGB" Output: 3 Explanation: RBYYBBRRB -> RBYY[Y]BBRRB -> RBBBRRB -> RRRB -> B -> B[B] -> BB[B] -> empty

 

Note:

1. You may assume that the initial row of balls on the table won’t have any 3 or more consecutive balls with the same color.
2. The number of balls on the table won't exceed 20, and the string represents these balls is called "board" in the input.
3. The number of balls in your hand won't exceed 5, and the string represents these balls is called "hand" in the input.
4. Both input strings will be non-empty and only contain characters 'R','Y','B','G','W'.

 

Approach #1: DFS. [My Code][Wrong].

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<code-pre class="code-pre code-pre-line" id="pre-Rfxnb6"><code-line class="line-numbers-rows"></code-line>class Solution { <code-line class="line-numbers-rows"></code-line>    int ret = Integer.MAX_VALUE; <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public int findMinStep(String board, String hand) { <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        dfs(board, hand, 0); <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        return ret == Integer.MAX_VALUE ? -1 : ret; <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public void dfs(String board, String hand, int cur) { <code-line class="line-numbers-rows"></code-line>        if (dontHave(hand) && board.length() != 0) return; <code-line class="line-numbers-rows"></code-line>        if (board == null && board.length() == 0) <code-line class="line-numbers-rows"></code-line>            ret = Math.min(ret, cur); <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        if (board.length() < 2 && inHand(hand, board.charAt(0))) { <code-line class="line-numbers-rows"></code-line>            board += board.charAt(0); <code-line class="line-numbers-rows"></code-line>            dfs(board, hand, cur+1); <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        for (int i = 1; i < board.length(); ++i) { <code-line class="line-numbers-rows"></code-line>            StringBuilder copy = new StringBuilder(board); <code-line class="line-numbers-rows"></code-line>            boolean isChange = false; <code-line class="line-numbers-rows"></code-line> <code-line class="line-numbers-rows"></code-line>            if (board.charAt(i) == board.charAt(i-1) && inHand(hand, board.charAt(i))) { <code-line class="line-numbers-rows"></code-line>                copy.deleteCharAt(i-1); <code-line class="line-numbers-rows"></code-line>                copy.deleteCharAt(i-1); <code-line class="line-numbers-rows"></code-line>                String temp = trim(copy); <code-line class="line-numbers-rows"></code-line>                dfs(temp, hand, cur+1); <code-line class="line-numbers-rows"></code-line>                isChange = true; <code-line class="line-numbers-rows"></code-line>            } <code-line class="line-numbers-rows"></code-line>            <code-line class="line-numbers-rows"></code-line>            // recover <code-line class="line-numbers-rows"></code-line>            if (isChange) { <code-line class="line-numbers-rows"></code-line>                hand += board.charAt(i); <code-line class="line-numbers-rows"></code-line>            } <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public String trim(StringBuilder temp) { <code-line class="line-numbers-rows"></code-line>        if (temp == null || temp.length() == 0) return ""; <code-line class="line-numbers-rows"></code-line>        int count = 1; <code-line class="line-numbers-rows"></code-line>        for (int i = 1; i < temp.length(); ++i) { <code-line class="line-numbers-rows"></code-line>            if (temp.charAt(i-1) == temp.charAt(i)) { <code-line class="line-numbers-rows"></code-line>                count++; <code-line class="line-numbers-rows"></code-line>            } else { <code-line class="line-numbers-rows"></code-line>                if (count >= 3) { <code-line class="line-numbers-rows"></code-line>                    int lastPos = i - count; <code-line class="line-numbers-rows"></code-line>                    return trim(temp.delete(lastPos, i)); <code-line class="line-numbers-rows"></code-line>                } <code-line class="line-numbers-rows"></code-line>                count = 1; <code-line class="line-numbers-rows"></code-line>            } <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>        return temp.toString(); <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public boolean inHand(String hand, Character c) { <code-line class="line-numbers-rows"></code-line>        for (int i = 0; i < hand.length(); ++i) { <code-line class="line-numbers-rows"></code-line>            if (hand.charAt(i) == c) { <code-line class="line-numbers-rows"></code-line>                hand.charAt(i) = '#'; <code-line class="line-numbers-rows"></code-line>                return true; <code-line class="line-numbers-rows"></code-line>            } <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>        return false; <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public boolean dontHave(String hand) { <code-line class="line-numbers-rows"></code-line>        for (int i = 0; i < hand.length(); ++i) { <code-line class="line-numbers-rows"></code-line>            if (hand.charAt(i) != '#') return false; <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>        return true; <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>} </code-pre>

　　

Approach #2: DFS. [Java]

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<code-pre class="code-pre code-pre-line" id="pre-n62Trs"><code-line class="line-numbers-rows"></code-line>class Solution { <code-line class="line-numbers-rows"></code-line>    int MaxNum = 6; <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public int findMinStep(String board, String hand) { <code-line class="line-numbers-rows"></code-line>        int ret = MaxNum; <code-line class="line-numbers-rows"></code-line>        int[] handCount = new int[26]; <code-line class="line-numbers-rows"></code-line>        for (int i = 0; i < hand.length(); ++i) <code-line class="line-numbers-rows"></code-line>            handCount[hand.charAt(i) - 'A']++; <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        ret = dfs(board+"#", handCount); <code-line class="line-numbers-rows"></code-line>        <code-line class="line-numbers-rows"></code-line>        return ret == MaxNum ? -1 : ret; <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public int dfs(String s, int[] h) { <code-line class="line-numbers-rows"></code-line>        s = removeConsecutives(s); <code-line class="line-numbers-rows"></code-line>        if (s.equals("#")) return 0; <code-line class="line-numbers-rows"></code-line>        int rs = MaxNum, need = 0; <code-line class="line-numbers-rows"></code-line>        for (int i = 0, j = 0; j < s.length(); ++j) { <code-line class="line-numbers-rows"></code-line>            if (s.charAt(i) == s.charAt(j)) continue; <code-line class="line-numbers-rows"></code-line>            need = 3 - (j - i); <code-line class="line-numbers-rows"></code-line>            if (h[s.charAt(i)-'A'] >= need) { <code-line class="line-numbers-rows"></code-line>                h[s.charAt(i)-'A'] -= need; <code-line class="line-numbers-rows"></code-line>                rs = Math.min(rs, need + dfs(s.substring(0, i) + s.substring(j), h)); <code-line class="line-numbers-rows"></code-line>                h[s.charAt(i)-'A'] += need; <code-line class="line-numbers-rows"></code-line>            } <code-line class="line-numbers-rows"></code-line>            i = j; <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>        return rs; <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    public String removeConsecutives(String s) { <code-line class="line-numbers-rows"></code-line>        for (int i = 0, j = 0; j < s.length(); ++j) { <code-line class="line-numbers-rows"></code-line>            if (s.charAt(i) == s.charAt(j)) continue; <code-line class="line-numbers-rows"></code-line>            if (j - i >= 3) { <code-line class="line-numbers-rows"></code-line>                return removeConsecutives(s.substring(0, i) + s.substring(j)); <code-line class="line-numbers-rows"></code-line>            } else i = j; <code-line class="line-numbers-rows"></code-line>        } <code-line class="line-numbers-rows"></code-line>        return s; <code-line class="line-numbers-rows"></code-line>    } <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>    <code-line class="line-numbers-rows"></code-line>} </code-pre>

　　

Reference:

https://leetcode.com/problems/zuma-game/discuss/97010/%22short%22-java-solution-beats-98

 

__EOF__

本文作者：Veritas des Liberty
本文链接：https://www.cnblogs.com/h-hkai/p/10957569.html
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