1

454

pom.xml

@@ -17,6 +17,11 @@
 <dependencies>
 
 
+	<dependency>
+		<groupId>cn.hutool</groupId>
+		<artifactId>hutool-http</artifactId>
+		<version>5.8.18</version>
+	</dependency>
 
 
 	<dependency>

src/main/java/cn/whaifree/leetCode/Hash/LeetCode383.java

@@ -0,0 +1,94 @@
+package cn.whaifree.leetCode.Hash;
+
+import cn.hutool.core.map.MapUtil;
+import cn.whaifree.leetCode.utils.MapUtils;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * 383. 赎金信
+
+ * 给你两个字符串：ransomNote 和 magazine ，判断 ransomNote 能不能由 magazine 里面的字符构成。
+ *
+ * 如果可以，返回 true ；否则返回 false 。
+ *
+ * magazine 中的每个字符只能在 ransomNote 中使用一次。
+ *
+ * 示例 1：
+ *
+ * 输入：ransomNote = "a", magazine = "b"
+ * 输出：false
+ * 示例 2：
+ *
+ * 输入：ransomNote = "aa", magazine = "ab"
+ * 输出：false
+ * 示例 3：
+ *
+ * 输入：ransomNote = "aa", magazine = "aab"
+ * 输出：true
+ *
+ *
+ * 提示：
+ *
+ * 1 <= ransomNote.length, magazine.length <= 105
+ * ransomNote 和 magazine 由小写英文字母组成
+ */
+public class LeetCode383 {
+
+    @Test
+    public void test() {
+        boolean b = new Solution1().canConstruct("aabb", "aabbc");
+        System.out.println(b);
+    }
+
+    class Solution {
+        public boolean canConstruct(String ransomNote, String magazine) {
+
+            Map<Character, Integer> mapR  = new HashMap<>();
+            for (char c : ransomNote.toCharArray()) {
+                mapR.put(c, mapR.getOrDefault(c, 0) + 1);
+            }
+
+            Map<Character, Integer> mapM = new HashMap<>();
+            for (char c : magazine.toCharArray()) {
+                mapM.put(c, mapM.getOrDefault(c, 0) + 1);
+            }
+
+
+            MapUtils.printMap(mapR);
+            MapUtils.printMap(mapM);
+
+            for (Character c : mapR.keySet()) {
+                if (mapM.getOrDefault(c, 0) < mapR.getOrDefault(c, 0)) {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+    }
+
+    class Solution1 {
+
+        // ransomNote 和 magazine 由小写英文字母组成
+        public boolean canConstruct(String ransomNote, String magazine) {
+            int[] map = new int[26];
+            // 大的先存入Map
+
+            // 相比转换为Char更快
+            for (int i = 0; i < magazine.length(); i++) map[magazine.charAt(i) - 'a'] += 1;
+            // 减去小的如果小于0，如果不够减就返回false
+            for (int i = 0; i < ransomNote.length(); i++) {
+                int index = ransomNote.charAt(i) - 97;
+                map[index] -= 1;
+                if (map[index] < 0) {
+                    return false;
+                }
+            }
+
+            return true;
+        }
+    }
+}

src/main/java/cn/whaifree/leetCode/LinkedList/LeetCode2487.java

@@ -0,0 +1,98 @@
+package cn.whaifree.leetCode.LinkedList;
+
+import cn.whaifree.leetCode.model.ListNode;
+import org.junit.Test;
+
+public class LeetCode2487 {
+    @Test
+    public void test() {
+        new Solution1().removeNodes(ListNode.listNodeFromArray(new int[]{5, 2, 13, 3, 8})).printList();
+    }
+
+
+    /**
+     * 找到最大的节点，找到下一个最大的节点，此区间全部删掉。
+     *   每次删除后MaxNode为null
+     *
+     *   即最后变成了递减的链表
+     *
+     */
+    class Solution {
+        /**
+         * 递归
+         * @param head
+         * @return
+         */
+//        public ListNode removeNodes(ListNode head) {
+//            ListNode dummy = new ListNode(0, head);
+//            ListNode pre = dummy;
+//            ListNode index = head;
+//            ListNode maxNode = dummy;
+//            while (index != null) {
+//                if (index.val > maxNode.val) {
+//                    maxNode = index;
+//                    // 删除pre到maxNode的前一个节点
+//                    pre.next = maxNode;
+//                    maxNode.next = removeNodes(maxNode.next);
+//                }
+//                index = index.next;
+//            }
+//
+//            return dummy.next;
+//        }
+        public ListNode removeNodes(ListNode head) {
+            return remove(new ListNode(0, head));
+        }
+
+        public ListNode remove(ListNode head) {
+            if (head == null) {
+                return null;
+            }
+
+            head.next = remove(head.next);
+            if (head.next != null && head.val < head.next.val) {
+                return head.next;
+            } else {
+                return head;
+            }
+        }
+
+    }
+
+    class Solution1 {
+
+
+        public ListNode removeNodes(ListNode head) {
+
+            ListNode newHead = reverse(head);
+            // 变成从右往左边移除比newHead小的
+            ListNode index = newHead;
+            ListNode tmpMaxNode = newHead;
+            while (index.next != null) {
+                if (index.next.val < tmpMaxNode.val) {
+                    index.next = index.next.next;
+                } else {
+                    index = index.next;
+                    tmpMaxNode = index;
+                }
+            }
+            // 最后那个数是永远不会删除的
+            return reverse(newHead);
+        }
+
+        public ListNode reverse(ListNode head) {
+            // 反转链表
+            ListNode index = head;
+            ListNode pre = null;
+
+            while (index != null) {
+                ListNode tmp = index.next;
+                index.next = pre;
+                pre = index;
+                index = tmp;
+            }
+            // {5, 2, 13, 3, 8}
+            return pre;
+        }
+    }
+}

src/main/java/cn/whaifree/leetCode/model/ListNode.java

@@ -45,7 +45,10 @@ public class ListNode {
             System.out.print(curr.val + " ");
             curr = curr.next;
         }
+    }
 
+    public void printList() {
+        printList(this);
     }
 
 }

src/main/java/cn/whaifree/leetCode/utils/MapUtils.java

@@ -0,0 +1,16 @@
+package cn.whaifree.leetCode.utils;
+
+import java.util.Map;
+
+public class MapUtils {
+
+    public  static void printMap(Map map) {
+        if (map == null) {
+            return;
+        }
+        for (Object key : map.keySet()) {
+            System.out.println(key + " : " + map.get(key));
+        }
+        System.out.println("==========");
+    }
+}