modify code

src/class22/Code01_KillMonster.java

@@ -2,72 +2,78 @@ package class22;
 
 public class Code01_KillMonster {
 
-	public static double right1(int N, int M, int K) {
+	public static double right(int N, int M, int K) {
 		if (N < 1 || M < 1 || K < 1) {
 			return 0;
 		}
 		long all = (long) Math.pow(M + 1, K);
-		long kill = process1(N, M, K);
+		long kill = process(K, M, N);
 		return (double) ((double) kill / (double) all);
 	}
 
-	public static long process1(int N, int M, int K) {
-		if (K == 0) {
-			return N <= 0 ? 1 : 0;
+	// 怪兽还剩hp点血
+	// 每次的伤害在[0~M]范围上
+	// 还有times次可以砍
+	// 返回砍死的情况数！
+	public static long process(int times, int M, int hp) {
+		if (times == 0) {
+			return hp <= 0 ? 1 : 0;
+		}
+		if (hp <= 0) {
+			return (long) Math.pow(M + 1, times);
 		}
 		long ways = 0;
 		for (int i = 0; i <= M; i++) {
-			ways += process1(N - i, M, K - 1);
+			ways += process(times - 1, M, hp - i);
 		}
 		return ways;
 	}
 
-	public static double right2(int N, int M, int K) {
+	public static double dp1(int N, int M, int K) {
 		if (N < 1 || M < 1 || K < 1) {
 			return 0;
 		}
 		long all = (long) Math.pow(M + 1, K);
-		long kill = process2(N, M, K);
-		return (double) ((double) kill / (double) all);
-	}
-
-	public static long process2(int N, int M, int K) {
-		if (K == 0) {
-			return N <= 0 ? 1 : 0;
-		}
-		if (N <= 0) {
-			return (long) (Math.pow(M + 1, K));
+		long[][] dp = new long[K + 1][N + 1];
+		dp[0][0] = 1;
+		for (int times = 1; times <= K; times++) {
+			dp[times][0] = (long) Math.pow(M + 1, times);
+			for (int hp = 1; hp <= N; hp++) {
+				long ways = 0;
+				for (int i = 0; i <= M; i++) {
+					if (hp - i >= 0) {
+						ways += dp[times - 1][hp - i];
+					} else {
+						ways += (long) Math.pow(M + 1, times - 1);
+					}
+				}
+				dp[times][hp] = ways;
+			}
 		}
-		return process2(N, M, K - 1) + process2(N - 1, M, K) - process2(N - M - 1, M, K - 1);
+		long kill = dp[K][N];
+		return (double) ((double) kill / (double) all);
 	}
 
-	// M = 5
-	// 以下为斜率优化改进枚举行为的动态规划
-	// dp[8][5] = dp[8..3][4]
-	// dp[9][5] = dp[9..4][4] = dp[9][4] + dp[8][5] - dp[3][4]
-	// 可以推出
-	// dp[i][j] = dp[i][j-1] + dp[i-1][j] - dp[i - M - 1][j-1]
-	public static double dp(int N, int M, int K) {
+	public static double dp2(int N, int M, int K) {
 		if (N < 1 || M < 1 || K < 1) {
 			return 0;
 		}
-		long[][] dp = new long[N + 1][K + 1];
-		// 特别注意：dp[0][j]既表示原含义，也表示M+1的j次方的值
+		long all = (long) Math.pow(M + 1, K);
+		long[][] dp = new long[K + 1][N + 1];
 		dp[0][0] = 1;
-		for (int j = 1; j <= K; j++) {
-			dp[0][j] = dp[0][j - 1] * (M + 1);
-		}
-		for (int j = 1; j <= K; j++) {
-			for (int i = 1; i <= N; i++) {
-				dp[i][j] = dp[i][j - 1] + dp[i - 1][j];
-				if (i - M - 1 < 0) {
-					dp[i][j] -= dp[0][j - 1];
+		for (int times = 1; times <= K; times++) {
+			dp[times][0] = (long) Math.pow(M + 1, times);
+			for (int hp = 1; hp <= N; hp++) {
+				dp[times][hp] = dp[times][hp - 1] + dp[times - 1][hp];
+				if (hp - 1 - M >= 0) {
+					dp[times][hp] -= dp[times - 1][hp - 1 - M];
 				} else {
-					dp[i][j] -= dp[i - M - 1][j - 1];
+					dp[times][hp] -= Math.pow(M + 1, times - 1);
 				}
 			}
 		}
-		return (double) ((double) dp[N][K] / (double) dp[0][K]);
+		long kill = dp[K][N];
+		return (double) ((double) kill / (double) all);
 	}
 
 	public static void main(String[] args) {
@@ -80,9 +86,9 @@ public class Code01_KillMonster {
 			int N = (int) (Math.random() * NMax);
 			int M = (int) (Math.random() * MMax);
 			int K = (int) (Math.random() * KMax);
-			double ans1 = right1(N, M, K);
-			double ans2 = right2(N, M, K);
-			double ans3 = dp(N, M, K);
+			double ans1 = right(N, M, K);
+			double ans2 = dp1(N, M, K);
+			double ans3 = dp2(N, M, K);
 			if (ans1 != ans2 || ans1 != ans3) {
 				System.out.println("Oops!");
 				break;

src/class22/Code02_MinCoinsNoLimit.java

@@ -6,10 +6,10 @@ public class Code02_MinCoinsNoLimit {
 		return process(arr, 0, aim);
 	}
 
+	// arr[index...]面值，每种面值张数自由选择，
+	// 搞出rest正好这么多钱，返回最小张数
+	// 拿Integer.MAX_VALUE标记怎么都搞定不了
 	public static int process(int[] arr, int index, int rest) {
-		if (rest < 0) {
-			return Integer.MAX_VALUE;
-		}
 		if (index == arr.length) {
 			return rest == 0 ? 0 : Integer.MAX_VALUE;
 		} else {
@@ -17,14 +17,39 @@ public class Code02_MinCoinsNoLimit {
 			for (int zhang = 0; zhang * arr[index] <= rest; zhang++) {
 				int next = process(arr, index + 1, rest - zhang * arr[index]);
 				if (next != Integer.MAX_VALUE) {
-					ans = Math.min(ans, next + zhang);
+					ans = Math.min(ans, zhang + next);
 				}
 			}
 			return ans;
 		}
 	}
 
-	public static int dp(int[] arr, int aim) {
+	public static int dp1(int[] arr, int aim) {
+		if (aim == 0) {
+			return 0;
+		}
+		int N = arr.length;
+		int[][] dp = new int[N + 1][aim + 1];
+		dp[N][0] = 0;
+		for (int j = 1; j <= aim; j++) {
+			dp[N][j] = Integer.MAX_VALUE;
+		}
+		for (int index = N - 1; index >= 0; index--) {
+			for (int rest = 0; rest <= aim; rest++) {
+				int ans = Integer.MAX_VALUE;
+				for (int zhang = 0; zhang * arr[index] <= rest; zhang++) {
+					int next = dp[index + 1][rest - zhang * arr[index]];
+					if (next != Integer.MAX_VALUE) {
+						ans = Math.min(ans, zhang + next);
+					}
+				}
+				dp[index][rest] = ans;
+			}
+		}
+		return dp[0][aim];
+	}
+
+	public static int dp2(int[] arr, int aim) {
 		if (aim == 0) {
 			return 0;
 		}
@@ -37,8 +62,10 @@ public class Code02_MinCoinsNoLimit {
 		for (int index = N - 1; index >= 0; index--) {
 			for (int rest = 0; rest <= aim; rest++) {
 				dp[index][rest] = dp[index + 1][rest];
-				if (rest - arr[index] >= 0 && dp[index][rest - arr[index]] != Integer.MAX_VALUE)
+				if (rest - arr[index] >= 0 
+						&& dp[index][rest - arr[index]] != Integer.MAX_VALUE) {
 					dp[index][rest] = Math.min(dp[index][rest], dp[index][rest - arr[index]] + 1);
+				}
 			}
 		}
 		return dp[0][aim];
@@ -77,8 +104,9 @@ public class Code02_MinCoinsNoLimit {
 			int[] arr = randomArray(N, maxValue);
 			int aim = (int) (Math.random() * maxValue);
 			int ans1 = minCoins(arr, aim);
-			int ans2 = dp(arr, aim);
-			if (ans1 != ans2) {
+			int ans2 = dp1(arr, aim);
+			int ans3 = dp2(arr, aim);
+			if (ans1 != ans2 || ans1 != ans3) {
 				System.out.println("Oops!");
 				printArray(arr);
 				System.out.println(aim);

src/class22/Code03_SplitNumber.java

@@ -0,0 +1,85 @@
+package class22;
+
+public class Code03_SplitNumber {
+
+	// n为正数
+	public static int ways(int n) {
+		if (n < 0) {
+			return 0;
+		}
+		if (n == 1) {
+			return 1;
+		}
+		return process(1, n);
+	}
+
+	// 上一个拆出来的数是pre
+	// 还剩rest需要去拆
+	// 返回拆解的方法数
+	public static int process(int pre, int rest) {
+		if (rest == 0) {
+			return 1;
+		}
+		if (pre > rest) {
+			return 0;
+		}
+		int ways = 0;
+		for (int first = pre; first <= rest; first++) {
+			ways += process(first, rest - first);
+		}
+		return ways;
+	}
+
+	public static int dp1(int n) {
+		if (n < 0) {
+			return 0;
+		}
+		if (n == 1) {
+			return 1;
+		}
+		int[][] dp = new int[n + 1][n + 1];
+		for (int pre = 1; pre <= n; pre++) {
+			dp[pre][0] = 1;
+			dp[pre][pre] = 1;
+		}
+		for (int pre = n - 1; pre >= 1; pre--) {
+			for (int rest = pre + 1; rest <= n; rest++) {
+				int ways = 0;
+				for (int first = pre; first <= rest; first++) {
+					ways += dp[first][rest - first];
+				}
+				dp[pre][rest] = ways;
+			}
+		}
+		return dp[1][n];
+	}
+
+	public static int dp2(int n) {
+		if (n < 0) {
+			return 0;
+		}
+		if (n == 1) {
+			return 1;
+		}
+		int[][] dp = new int[n + 1][n + 1];
+		for (int pre = 1; pre <= n; pre++) {
+			dp[pre][0] = 1;
+			dp[pre][pre] = 1;
+		}
+		for (int pre = n - 1; pre >= 1; pre--) {
+			for (int rest = pre + 1; rest <= n; rest++) {
+				dp[pre][rest] = dp[pre + 1][rest];
+				dp[pre][rest] += dp[pre][rest - pre];
+			}
+		}
+		return dp[1][n];
+	}
+
+	public static void main(String[] args) {
+		int test = 39;
+		System.out.println(ways(test));
+		System.out.println(dp1(test));
+		System.out.println(dp2(test));
+	}
+
+}

src/class23/Code01_SplitSumClosed.java

@@ -1,8 +1,8 @@
-package class22;
+package class23;
 
 import java.util.TreeSet;
 
-public class Code03_SplitSumClosed {
+public class Code01_SplitSumClosed {
 
 	public static int right(int[] arr) {
 		if (arr == null || arr.length < 2) {

src/class23/Code02_SplitSumClosedSizeHalf.java

@@ -1,8 +1,8 @@
-package class22;
+package class23;
 
 import java.util.TreeSet;
 
-public class Code04_SplitSumClosedSizeHalf {
+public class Code02_SplitSumClosedSizeHalf {
 
 	public static int right(int[] arr) {
 		if (arr == null || arr.length < 2) {

src/class23/Code03_NQueens.java

@@ -1,6 +1,6 @@
 package class23;
 
-public class Code01_NQueens {
+public class Code03_NQueens {
 
 	public static int num1(int n) {
 		if (n < 1) {

src/class23/Code04_MinCoinsOnePaper.java

@@ -4,7 +4,7 @@ import java.util.HashMap;
 import java.util.Map.Entry;
 import java.util.LinkedList;
 
-public class Code02_MinCoinsOnePaper {
+public class Code04_MinCoinsOnePaper {
 
 	public static int minCoins(int[] arr, int aim) {
 		return process(arr, 0, aim);