Merge branch 'main' into dev

en/codes/java/.gitignore

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+build

en/codes/java/chapter_array_and_linkedlist/array.java

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+/**
+ * File: array.java
+ * Created Time: 2022-11-25
+ * Author: krahets ([email protected])
+ */
+
+package chapter_array_and_linkedlist;
+
+import java.util.*;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class array {
+    /* Random access to elements */
+    static int randomAccess(int[] nums) {
+        // Randomly select a number in the interval [0, nums.length)
+        int randomIndex = ThreadLocalRandom.current().nextInt(0, nums.length);
+        // Retrieve and return a random element
+        int randomNum = nums[randomIndex];
+        return randomNum;
+    }
+
+    /* Extend array length */
+    static int[] extend(int[] nums, int enlarge) {
+        // Initialize an extended length array
+        int[] res = new int[nums.length + enlarge];
+        // Copy all elements from the original array to the new array
+        for (int i = 0; i < nums.length; i++) {
+            res[i] = nums[i];
+        }
+        // Return the new array after expansion
+        return res;
+    }
+
+    /* Insert element num at `index` */
+    static void insert(int[] nums, int num, int index) {
+        // Move all elements after `index` one position backward
+        for (int i = nums.length - 1; i > index; i--) {
+            nums[i] = nums[i - 1];
+        }
+        // Assign num to the element at index
+        nums[index] = num;
+    }
+
+    /* Remove the element at `index` */
+    static void remove(int[] nums, int index) {
+        // Move all elements after `index` one position forward
+        for (int i = index; i < nums.length - 1; i++) {
+            nums[i] = nums[i + 1];
+        }
+    }
+
+    /* Traverse array */
+    static void traverse(int[] nums) {
+        int count = 0;
+        // Traverse array by index
+        for (int i = 0; i < nums.length; i++) {
+            count += nums[i];
+        }
+        // Traverse array elements
+        for (int num : nums) {
+            count += num;
+        }
+    }
+
+    /* Search for a specified element in the array */
+    static int find(int[] nums, int target) {
+        for (int i = 0; i < nums.length; i++) {
+            if (nums[i] == target)
+                return i;
+        }
+        return -1;
+    }
+
+    /* Driver Code */
+    public static void main(String[] args) {
+        /* Initialize an array */
+        int[] arr = new int[5];
+        System.out.println("Array arr = " + Arrays.toString(arr));
+        int[] nums = { 1, 3, 2, 5, 4 };
+        System.out.println("Array nums = " + Arrays.toString(nums));
+
+        /* Random access */
+        int randomNum = randomAccess(nums);
+        System.out.println("Get a random element from nums = " + randomNum);
+
+        /* Length extension */
+        nums = extend(nums, 3);
+        System.out.println("Extend the array length to 8, resulting in nums = " + Arrays.toString(nums));
+
+        /* Insert element */
+        insert(nums, 6, 3);
+        System.out.println("Insert the number 6 at index 3, resulting in nums = " + Arrays.toString(nums));
+
+        /* Remove element */
+        remove(nums, 2);
+        System.out.println("Remove the element at index 2, resulting in nums = " + Arrays.toString(nums));
+
+        /* Traverse array */
+        traverse(nums);
+
+        /* Search for elements */
+        int index = find(nums, 3);
+        System.out.println("Find element 3 in nums, index = " + index);
+    }
+}

en/codes/java/chapter_array_and_linkedlist/linked_list.java

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+/**
+ * File: linked_list.java
+ * Created Time: 2022-11-25
+ * Author: krahets ([email protected])
+ */
+
+package chapter_array_and_linkedlist;
+
+import utils.*;
+
+public class linked_list {
+    /* Insert node P after node n0 in the linked list */
+    static void insert(ListNode n0, ListNode P) {
+        ListNode n1 = n0.next;
+        P.next = n1;
+        n0.next = P;
+    }
+
+    /* Remove the first node after node n0 in the linked list */
+    static void remove(ListNode n0) {
+        if (n0.next == null)
+            return;
+        // n0 -> P -> n1
+        ListNode P = n0.next;
+        ListNode n1 = P.next;
+        n0.next = n1;
+    }
+
+    /* Access the node at `index` in the linked list */
+    static ListNode access(ListNode head, int index) {
+        for (int i = 0; i < index; i++) {
+            if (head == null)
+                return null;
+            head = head.next;
+        }
+        return head;
+    }
+
+    /* Search for the first node with value target in the linked list */
+    static int find(ListNode head, int target) {
+        int index = 0;
+        while (head != null) {
+            if (head.val == target)
+                return index;
+            head = head.next;
+            index++;
+        }
+        return -1;
+    }
+
+    /* Driver Code */
+    public static void main(String[] args) {
+        /* Initialize linked list */
+        // Initialize each node
+        ListNode n0 = new ListNode(1);
+        ListNode n1 = new ListNode(3);
+        ListNode n2 = new ListNode(2);
+        ListNode n3 = new ListNode(5);
+        ListNode n4 = new ListNode(4);
+        // Build references between nodes
+        n0.next = n1;
+        n1.next = n2;
+        n2.next = n3;
+        n3.next = n4;
+        System.out.println("The initialized linked list is");
+        PrintUtil.printLinkedList(n0);
+
+        /* Insert node */
+        insert(n0, new ListNode(0));
+        System.out.println("Linked list after inserting the node is");
+        PrintUtil.printLinkedList(n0);
+
+        /* Remove node */
+        remove(n0);
+        System.out.println("Linked list after removing the node is");
+        PrintUtil.printLinkedList(n0);
+
+        /* Access node */
+        ListNode node = access(n0, 3);
+        System.out.println("The value of the node at index 3 in the linked list = " + node.val);
+
+        /* Search node */
+        int index = find(n0, 2);
+        System.out.println("The index of the node with value 2 in the linked list = " + index);
+    }
+}

en/codes/java/chapter_array_and_linkedlist/list.java

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+/**
+ * File: list.java
+ * Created Time: 2022-11-25
+ * Author: krahets ([email protected])
+ */
+
+package chapter_array_and_linkedlist;
+
+import java.util.*;
+
+public class list {
+    public static void main(String[] args) {
+        /* Initialize list */
+        // The array's element type is Integer[], a wrapper class for int
+        Integer[] numbers = new Integer[] { 1, 3, 2, 5, 4 };
+        List<Integer> nums = new ArrayList<>(Arrays.asList(numbers));
+        System.out.println("List nums = " + nums);
+
+        /* Access element */
+        int num = nums.get(1);
+        System.out.println("Access the element at index 1, obtained num = " + num);
+
+        /* Update element */
+        nums.set(1, 0);
+        System.out.println("Update the element at index 1 to 0, resulting in nums = " + nums);
+
+        /* Clear list */
+        nums.clear();
+        System.out.println("After clearing the list, nums = " + nums);
+
+        /* Add element at the end */
+        nums.add(1);
+        nums.add(3);
+        nums.add(2);
+        nums.add(5);
+        nums.add(4);
+        System.out.println("After adding elements, nums = " + nums);
+
+        /* Insert element in the middle */
+        nums.add(3, 6);
+        System.out.println("Insert the number 6 at index 3, resulting in nums = " + nums);
+
+        /* Remove element */
+        nums.remove(3);
+        System.out.println("Remove the element at index 3, resulting in nums = " + nums);
+
+        /* Traverse the list by index */
+        int count = 0;
+        for (int i = 0; i < nums.size(); i++) {
+            count += nums.get(i);
+        }
+        /* Traverse the list elements */
+        for (int x : nums) {
+            count += x;
+        }
+
+        /* Concatenate two lists */
+        List<Integer> nums1 = new ArrayList<>(Arrays.asList(new Integer[] { 6, 8, 7, 10, 9 }));
+        nums.addAll(nums1);
+        System.out.println("Concatenate list nums1 to nums, resulting in nums = " + nums);
+
+        /* Sort list */
+        Collections.sort(nums);
+        System.out.println("After sorting the list, nums = " + nums);
+    }
+}