算法（三十二）

1、在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点保留一个，返回链表头指针。 例如，链表1->2->3->3->4->4->5 处理后为 1->2->5

private static ListNode fun2(ListNode head) {
    ListNode res = new ListNode(0);
    res.next = head;
    ListNode temp = head;
    ListNode res2 = res;

    while (temp!=null){
        if(temp.next!=null && temp.val == temp.next.val){
            while (temp.next!=null && temp.val == temp.next.val){
                temp =temp.next;
                res = res.next;
            }
            temp = temp.next;
            res.next = temp;
        }else{
            temp = temp.next;
            res = res.next;
        }
    }
    return res2.next;
}

2、输入一个字符串,按字典序打印出该字符串中字符的所有排列。例如输入字符串abc,则打印出由字符a,b,c所能排列出来的所有字符串abc,acb,bac,bca,cab和cba。

public class test012 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String str = sc.nextLine();
            char[] chars = str.toCharArray();
            ArrayList<String> list = new ArrayList<>();
            fun(chars, 0, list);
            for(int i=0; i<list.size(); i++){
                System.out.println(list.get(i));
            }
        }
    }

    private static void fun(char[] chars, int begin, ArrayList<String> list) {
        if(chars.length == 0 || chars == null || begin<0 || begin>chars.length){
            return;
        }
        if(begin == chars.length-1){
            list.add(String.valueOf(chars));
        }else{
            for(int i=begin; i<chars.length; i++){
                swap(chars, begin, i);
                fun(chars, begin+1, list);
                swap(chars, begin, i);
            }
        }
    }

    private static void swap(char[] chars, int i, int j) {
        char temp = chars[i];
        chars[i] = chars[j];
        chars[j] = temp;
    }