23. Merge k Sorted Lists

Question

23. Merge k Sorted Lists

Solution

题目大意：合并链表数组（每个链表中的元素是有序的），要求合并后的链表也是有序的

思路：遍历链表数组，每次取最小节点

Java实现：

public ListNode mergeKLists(ListNode[] lists) {
    ListNode preHead = new ListNode(0);
    ListNode minNode = getMinNode(lists);
    ListNode tmpNode = preHead;
    while (minNode != null) {
        tmpNode.next = minNode;
        tmpNode = minNode;
        minNode = getMinNode(lists);
    }
    return preHead.next;
}

ListNode getMinNode(ListNode[] lists) {
    int minIdx = -1;
    int minVal = 0;
    for (int i=0; i<lists.length; i++) {
        ListNode cur = lists[i];
        if (cur != null) {
            if (minIdx == -1 || cur.val < minVal) {
                minIdx = i;
                minVal = cur.val;
            }
        }
    }
    if (minIdx != -1) {
        ListNode tmpNode = lists[minIdx];
        lists[minIdx] = tmpNode.next;
        return tmpNode;
    }
    return null;
}