NC_22_MERGE_ARRAY-NC_23_PARTITION_LIST-NC_24_DELETEDUPLICATENODE

package org.example.interview.practice;

/**
 * @author xianzhe.ma
 * @date 2021/9/1
 */

public class NC_22_MERGE_ARRAY {
    public static void merge(int A[], int m, int B[], int n) {

        if (m == 0) {
            for (int i=0;i<B.length;i++) {
                A[i] = B[i];
            }

            return ;
        }
        int i=0;
        int j = 0;
        for (;i<m&&j<n;) {
            if (A[i] < B[j]) {
                i++;
            } else {
                moveBack(A,i, m);
                A[i] = B[j];
                j++;
            }
        }

        if (j<n) {
            int start = m + (n-j-1);
            for (;j<n;j++) {
                A[start] = B[j];
                start++;
            }
        }
    }

    private static void moveBack(int arr[], int start,int validLength) {
        for (int i=start;i<validLength;i++) {
            arr[i+1] = arr[i];
        }

    }

    public static void merge2(int A[], int m, int B[], int n) {

        int end = m + n - 1, i = m - 1, j = n - 1; //初始化 end,i,j
        while (end != 0 && i >= 0 && j >= 0) {
            if (A[i] > B[j]) {
                A[end--] = A[i--];  //从尾部开始
            } else {
                A[end--] = B[j--];
            }
        }
        while (j >= 0) {
            A[end--] = B[j--]; // i《0，复制B
        }
    }

    public static void main (String[] agrs) {
        int[] a = new int[2];
        a[0] = 2;
        int[] b = {1};

        merge2 (a,1,b,1);
    }

}

package org.example.interview.practice;


/**
 * @author xianzhe.ma
 * @date 2021/8/25
 */

public class NC_23_PARTITION_LIST {

    public static class ListNode {
    int val;
    ListNode next = null;
    public ListNode(int val) {
        this.val = val;
    }
  }

    public ListNode partition (ListNode head, int x) {
        // write code here
        ListNode small = new ListNode(0);
        ListNode smallHead = small;
        ListNode large = new ListNode(0);
        ListNode largeHead = large;

        while (head != null) {

            if(head.val<x){
                small.next = head;
                small = small.next;
            }else{
                large.next = head;
                large =large.next;
            }
            head = head.next;
        }

        //对链表进行指空处理
        large.next = null;
        //将链表连起来
        small.next = largeHead.next;
        //返回新链表
        return smallHead.next;
    }
}

package org.example.interview.practice;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.Set;

/**
 * @author xianzhe.ma
 * @date 2021/7/21
 */

public class NC_24_DELETEDUPLICATENODE {

    public static class ListNode {
        int val;
        ListNode next = null;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public static ListNode deleteDuplicates (ListNode head) {
        // write code here
        Deque<ListNode> deque = new ArrayDeque<>();
        while (head != null) {

            if (deque.isEmpty() || deque.peekLast().val != head.val) {
                deque.addLast(head);
                head = head.next;
            } else {
                while (head != null && deque.peekLast().val == head.val) {
                    head = head.next;
                }
                ListNode last = deque.removeLast();
                last = null;
            }

        }
        head = null;
        ListNode cur = null;
        while (!deque.isEmpty()) {
            ListNode node = deque.pollFirst();
            node.next = null;
            if (head == null) {
                head = node;
                cur = node;
            } else {
                cur.next = node;
                cur = cur.next;
            }

        }
        return head;
    }

    public static void main (String[] args) {
        ListNode node = new ListNode(1);
        ListNode two = new ListNode(2);
        node.next = two;
        ListNode three = new ListNode(2);
        two.next = three;

        ListNode result = deleteDuplicates(node);
        System.out.println(result.val);
    }
}

 

package org.example.interview.practice;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashSet;
import java.util.Set;

/**
 * @author xianzhe.ma
 * @date 2021/7/21
 */

public class NC_25_DELETEDUPLICATENODE_I {

    public static class ListNode {
        int val;
        ListNode next = null;

        public ListNode(int val) {
            this.val = val;
        }
    }

    public static ListNode deleteDuplicates (ListNode head) {
        // write code here
        Deque<ListNode> deque = new ArrayDeque<>();
        while (head != null) {

            if (deque.isEmpty() || deque.peekLast().val != head.val) {
                deque.addLast(head);
                head = head.next;
            } else {
                while (head != null && deque.peekLast().val == head.val) {
                    head = head.next;
                }
                // ListNode last = deque.removeLast();
                // last = null;
            }

        }
        head = null;
        ListNode cur = null;
        while (!deque.isEmpty()) {
            ListNode node = deque.pollFirst();
            node.next = null;
            if (head == null) {
                head = node;
                cur = node;
            } else {
                cur.next = node;
                cur = cur.next;
            }

        }
        return head;
    }

    public static void main (String[] args) {
        ListNode node = new ListNode(1);
        ListNode two = new ListNode(2);
        node.next = two;
        ListNode three = new ListNode(2);
        two.next = three;

        ListNode result = deleteDuplicates(node);
        System.out.println(result.val);
    }
}