leetcode/partition_list.java at master · mapan/leetcode · GitHub

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public class Solution {
    public ListNode partition(ListNode head, int x) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ListNode root = new ListNode(-1);
        ListNode pivot = new ListNode(0);
        ListNode root_last = root, pivot_last = pivot;

        ListNode cur_node = head;
        while (cur_node != null) {
            //ListNode next = cur_node.next;
            if (cur_node.val < x) {
                root_last.next = cur_node;
                root_last = cur_node;
            } else {
                pivot_last.next = cur_node;
                pivot_last = cur_node;
                //pivot_last.next = null;
            }
            cur_node = cur_node.next;
        }
        pivot_last.next = null;
        root_last.next = pivot.next;

        return root.next;
    }
}

public ListNode partition(ListNode head, int x) {
    ListNode root = new ListNode(-1);
    ListNode pivot = new ListNode(x);
    ListNode root_last = root, pivot_last = pivot;

    ListNode cur_node = head;
    while (cur_node != null) {
        ListNode next = cur_node.next;
        if (cur_node.val < x) {
            root_last.next = cur_node;
            root_last = cur_node;
        } else {
            pivot_last.next = cur_node;
            pivot_last = cur_node;
            pivot_last.next = null;
        }
        cur_node = next;
    }
    root_last.next = pivot.next;

    return root.next;
}