摘要： 剑指Offer - 九度1348 - 数组中的逆序对2014-01-30 23:19题目描述：在数组中的两个数字，如果前面一个数字大于后面的数字，则这两个数字组成一个逆序对。输入一个数组，求出这个数组中的逆序对的总数。输入：每个测试案例包括两行：第一行包含一个整数n，表示数组中的元素个数。其中1 右半段的某个a[y]的话，那么a[x]、a[x+ 1]、...、a[j]必然都大于a[y]。 按上面那种算法，一次就多了j-x+1个逆序数。这么一来，就不用一个一个地算了。要是真一个一个地算逆序数，时间复杂度必然是O(n^2)了，因为逆序数本身就是O(n^2)数量级的。 最后，别忘了用64位整数来.. 阅读全文

摘要： Sort List2014.1.14 23:17Sort a linked list inO(nlogn) time using constant space complexity.Solution: The first thing I thought of about this problem is merge sort. It's weakness in space complexity is perfectly avoided with linked list, as you won't need another O(n) space when merging two s 阅读全文

摘要： Insertion Sort List2014.1.14 21:58Sort a linked list using insertion sort.Solution: Everyone must've have learned about insertion sort on some data structure textbooks, like "Data Structures & Algorithm Analysis". They usually present you with source code for insertion sort on arra 阅读全文

摘要： Binary Tree Postorder Traversal2014.1.14 21:17Given a binary tree, return thepostordertraversal of its nodes' values.For example:Given binary tree{1,#,2,3}, 1 \ 2 / 3return[3,2,1].Note:Recursive solution is trivial, could you do it iteratively?Solution1: Recursive solution is trivial,... 阅读全文

摘要： Binary Tree Preorder Traversal2014.1.14 02:36Given a binary tree, return thepreordertraversal of its nodes' values.For example:Given binary tree{1,#,2,3}, 1 \ 2 / 3return[1,2,3].Note:Recursive solution is trivial, could you do it iteratively?Solution1: The recursive version of preorde... 阅读全文

摘要： Reorder List2014.1.13 22:07Given a singly linked listL:L0→L1→…→Ln-1→Ln,reorder it to:L0→Ln→L1→Ln-1→L2→Ln-2→…You must do this in-place without altering the nodes' values.For example,Given{1,2,3,4}, reorder it to{1,4,2,3}.Solution1: My solution for this problem is in three steps: 1. cut the list i 阅读全文

摘要： Linked List Cycle II2014.1.13 21:43Given a linked list, return the node where the cycle begins. If there is no cycle, returnnull.Follow up:Can you solve it without using extra space?Solution: This problem doesn't only ask you to check if there is a loop in the list, but also to find out where yo 阅读全文

摘要： Linked List Cycle2014.1.13 21:24Given a linked list, determine if it has a cycle in it.Follow up:Can you solve it without using extra space?Solution: The problem indicated that you shouldn't use extra space. And you might be wondering why you should use extra space if you could just use two poin 阅读全文

摘要： Copy List with Random Pointer2014.1.13 20:45A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.Return a deep copy of the list.Solution: First of all, the problem description indicated that you have to return a deep copy. 阅读全文

摘要： Single Number II2014.1.13 20:25Given an array of integers, every element appearsthreetimes except for one. Find that single one.Note:Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?Solution: Still, exclusive OR is a wonderful operator. This.. 阅读全文