modify code

src/class39/Code01_SubsquenceMaxModM.java

@@ -1,10 +1,10 @@
-package class38;
+package class39;
 
 import java.util.HashSet;
 import java.util.TreeSet;
 
 // 给定一个非负数组arr，和一个正数m。 返回arr的所有子序列中累加和%m之后的最大值。
-public class Code05_SubsquenceMaxModM {
+public class Code01_SubsquenceMaxModM {
 
 	public static int max1(int[] arr, int m) {
 		HashSet<Integer> set = new HashSet<>();

src/class39/Code02_SnacksWays.java

@@ -0,0 +1,79 @@
+package class39;
+
+public class Code02_SnacksWays {
+
+	public static int ways1(int[] arr, int w) {
+		// arr[0...]
+		return process(arr, 0, w);
+	}
+
+	// 从左往右的经典模型
+	// 还剩的容量是rest，arr[index...]自由选择，
+	// 返回选择方案
+	// index ： 0～N
+	// rest : 0~w
+	public static int process(int[] arr, int index, int rest) {
+		if (rest < 0) { // 没有容量了
+			// -1 无方案的意思
+			return -1;
+		}
+		// rest>=0,
+		if (index == arr.length) { // 无零食可选
+			return 1;
+		}
+		// rest >=0
+		// 有零食index
+		// index号零食，要 or 不要
+		// index, rest
+		// (index+1, rest)
+		// (index+1, rest-arr[i])
+		int next1 = process(arr, index + 1, rest); // 不要
+		int next2 = process(arr, index + 1, rest - arr[index]); // 要
+		return next1 + (next2 == -1 ? 0 : next2);
+	}
+
+	public static int ways2(int[] arr, int w) {
+		int N = arr.length;
+		int[][] dp = new int[N + 1][w + 1];
+		for (int j = 0; j <= w; j++) {
+			dp[N][j] = 1;
+		}
+		for (int i = N - 1; i >= 0; i--) {
+			for (int j = 0; j <= w; j++) {
+				dp[i][j] = dp[i + 1][j] + ((j - arr[i] >= 0) ? dp[i + 1][j - arr[i]] : 0);
+			}
+		}
+		return dp[0][w];
+	}
+
+	public static int ways3(int[] arr, int w) {
+		int N = arr.length;
+		int[][] dp = new int[N][w + 1];
+		for (int i = 0; i < N; i++) {
+			dp[i][0] = 1;
+		}
+		if (arr[0] <= w) {
+			dp[0][arr[0]] = 1;
+		}
+		for (int i = 1; i < N; i++) {
+			for (int j = 1; j <= w; j++) {
+				dp[i][j] = dp[i - 1][j] + ((j - arr[i]) >= 0 ? dp[i - 1][j - arr[i]] : 0);
+			}
+		}
+		int ans = 0;
+		for (int j = 0; j <= w; j++) {
+			ans += dp[N - 1][j];
+		}
+		return ans;
+	}
+
+	public static void main(String[] args) {
+		int[] arr = { 4, 3, 2, 9 };
+		int w = 8;
+		System.out.println(ways1(arr, w));
+		System.out.println(ways2(arr, w));
+		System.out.println(ways3(arr, w));
+
+	}
+
+}

src/class39/Code02_SnacksWaysMain.java

@@ -0,0 +1,81 @@
+//不要拷贝包信息的内容
+package class39;
+
+//本文件是Code02_SnacksWays问题的牛客题目解答
+//但是用的分治的方法
+//这是牛客的测试链接：
+//https://www.nowcoder.com/questionTerminal/d94bb2fa461d42bcb4c0f2b94f5d4281
+//把如下的全部代码拷贝进编辑器（java）
+//可以直接通过
+import java.util.Map.Entry;
+import java.util.Scanner;
+import java.util.TreeMap;
+
+public class Code02_SnacksWaysMain {
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		int N = sc.nextInt();
+		int bag = sc.nextInt();
+		int[] arr = new int[N];
+		for (int i = 0; i < arr.length; i++) {
+			arr[i] = sc.nextInt();
+		}
+		long ways = ways(arr, bag);
+		System.out.println(ways);
+		sc.close();
+	}
+
+	public static long ways(int[] arr, int bag) {
+		if (arr == null || arr.length == 0) {
+			return 0;
+		}
+		if (arr.length == 1) {
+			return arr[0] <= bag ? 2 : 1;
+		}
+		int mid = (arr.length - 1) >> 1;
+		TreeMap<Long, Long> lmap = new TreeMap<>();
+		long ways = process(arr, 0, 0, mid, bag, lmap);
+		TreeMap<Long, Long> rmap = new TreeMap<>();
+		ways += process(arr, mid + 1, 0, arr.length - 1, bag, rmap);
+		TreeMap<Long, Long> rpre = new TreeMap<>();
+		long pre = 0;
+		for (Entry<Long, Long> entry : rmap.entrySet()) {
+			pre += entry.getValue();
+			rpre.put(entry.getKey(), pre);
+		}
+		for (Entry<Long, Long> entry : lmap.entrySet()) {
+			long lweight = entry.getKey();
+			long lways = entry.getValue();
+			Long floor = rpre.floorKey(bag - lweight);
+			if (floor != null) {
+				long rways = rpre.get(floor);
+				ways += lways * rways;
+			}
+		}
+		return ways + 1;
+	}
+
+	public static long process(int[] arr, int index, long w, int end, int bag, TreeMap<Long, Long> map) {
+		if (w > bag) {
+			return 0;
+		}
+		if (index > end) {
+			if (w != 0) {
+				if (!map.containsKey(w)) {
+					map.put(w, 1L);
+				} else {
+					map.put(w, map.get(w) + 1);
+				}
+				return 1;
+			} else {
+				return 0;
+			}
+		} else {
+			long ways = process(arr, index + 1, w, end, bag, map);
+			ways += process(arr, index + 1, w + arr[index], end, bag, map);
+			return ways;
+		}
+	}
+
+}

src/class39/Code03_10Ways.java

@@ -2,7 +2,7 @@ package class39;
 
 import java.util.LinkedList;
 
-public class Code02_10Ways {
+public class Code03_10Ways {
 
 	public static long ways1(int N) {
 		int zero = N;

src/class39/Code04_DifferentBTNum.java

@@ -1,6 +1,6 @@
 package class39;
 
-public class Code01_DifferentBTNum {
+public class Code04_DifferentBTNum {
 
 //	k(0) = 1, k(1) = 1
 //

src/class39/Code05_PrintMatrixSpiralOrder.java

@@ -1,6 +1,6 @@
 package class39;
 
-public class Code04_PrintMatrixSpiralOrder {
+public class Code05_PrintMatrixSpiralOrder {
 
 	public static void spiralOrderPrint(int[][] matrix) {
 		int tR = 0;

src/class39/Code06_RotateMatrix.java

@@ -1,6 +1,6 @@
 package class39;
 
-public class Code03_RotateMatrix {
+public class Code06_RotateMatrix {
 
 	public static void rotate(int[][] matrix) {
 		int a = 0;

src/class39/Code07_ZigZagPrintMatrix.java

@@ -1,6 +1,6 @@
 package class39;
 
-public class Code05_ZigZagPrintMatrix {
+public class Code07_ZigZagPrintMatrix {
 
 	public static void printMatrixZigZag(int[][] matrix) {
 		int tR = 0;

src/class39/Code08_PrintStar.java

@@ -1,6 +1,6 @@
 package class39;
 
-public class Code06_PrintStar {
+public class Code08_PrintStar {
 
 	public static void printStar(int N) {
 		int leftUp = 0;