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| 1 | +package class095; |
| 2 | + |
| 3 | +// 拿蛋糕 |
| 4 | +// 有a块草莓蛋糕,有b块芝士蛋糕,两人轮流拿蛋糕 |
| 5 | +// 每次不管是谁只能选择在草莓蛋糕和芝士蛋糕中拿一种 |
| 6 | +// 拿的数量在1~m之间随意,谁先拿完最后的蛋糕谁赢 |
| 7 | +// 返回先手赢还是后手赢 |
| 8 | +// 来自真实大厂笔试,没有在线测试,对数器验证 |
| 9 | +public class Code05_PickCakes { |
| 10 | + |
| 11 | + public static int MAXN = 151; |
| 12 | + |
| 13 | + public static String[][][] dp = new String[MAXN][MAXN][MAXN]; |
| 14 | + |
| 15 | + // 动态规划方法彻底尝试 |
| 16 | + // 为了验证 |
| 17 | + public static String win1(int a, int b, int m) { |
| 18 | + if (m >= Math.max(a, b)) { |
| 19 | + return a != b ? "先手" : "后手"; |
| 20 | + } |
| 21 | + if (a == b) { |
| 22 | + return "后手"; |
| 23 | + } |
| 24 | + if (dp[a][b][m] != null) { |
| 25 | + return dp[a][b][m]; |
| 26 | + } |
| 27 | + String ans = "后手"; |
| 28 | + for (int pick = 1; pick <= Math.min(a, m); pick++) { |
| 29 | + if (win1(a - pick, b, m).equals("后手")) { |
| 30 | + ans = "先手"; |
| 31 | + } |
| 32 | + if (ans.equals("先手")) { |
| 33 | + break; |
| 34 | + } |
| 35 | + } |
| 36 | + for (int pick = 1; pick <= Math.min(b, m); pick++) { |
| 37 | + if (win1(a, b - pick, m).equals("后手")) { |
| 38 | + ans = "先手"; |
| 39 | + } |
| 40 | + if (ans.equals("先手")) { |
| 41 | + break; |
| 42 | + } |
| 43 | + } |
| 44 | + dp[a][b][m] = ans; |
| 45 | + return ans; |
| 46 | + } |
| 47 | + |
| 48 | + // 正式方法 |
| 49 | + // 时间复杂度O(1) |
| 50 | + public static String win2(int a, int b, int m) { |
| 51 | + if (m >= Math.max(a, b)) { |
| 52 | + // nim博弈 |
| 53 | + return a != b ? "先手" : "后手"; |
| 54 | + } |
| 55 | + if (a == b) { |
| 56 | + return "后手"; |
| 57 | + } |
| 58 | + // 如果 a != b |
| 59 | + // 关注a和b的差值, |
| 60 | + // 谁最先遇到差值为0谁输 |
| 61 | + // 那么这就是巴什博奕 |
| 62 | + return (Math.max(a, b) - Math.min(a, b)) % (m + 1) != 0 ? "先手" : "后手"; |
| 63 | + } |
| 64 | + |
| 65 | + public static void main(String[] args) { |
| 66 | + System.out.println("测试开始"); |
| 67 | + for (int a = 0; a < MAXN; a++) { |
| 68 | + for (int b = 0; b < MAXN; b++) { |
| 69 | + for (int m = 0; m < MAXN; m++) { |
| 70 | + String ans1 = win1(a, b, m); |
| 71 | + String ans2 = win2(a, b, m); |
| 72 | + if (!ans1.equals(ans2)) { |
| 73 | + System.out.println("出错了!"); |
| 74 | + } |
| 75 | + } |
| 76 | + } |
| 77 | + } |
| 78 | + System.out.println("测试结束"); |
| 79 | + } |
| 80 | + |
| 81 | +} |
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