随笔分类 -  遍历

65. Valid Number
摘要：The general solution would be to check each char in turn and report the first char that makes the string a non number. There are some exceptions to wa 阅读全文
posted @ 2017-11-13 06:17 apanda009 阅读(178) 评论(0) 推荐(0)
556. Next Greater Element III
摘要：This solution is just a java version derived from this post. At first, lets look at the edge cases - Now the main algorithm works in following steps - 阅读全文
posted @ 2017-10-16 02:17 apanda009 阅读(152) 评论(0) 推荐(0)
451. Sort Characters By Frequency
摘要：Example 2: Example 3: The logic is very similar to NO.347 and here we just use a map a count and according to the frequency to put it into the right b 阅读全文
posted @ 2017-09-23 11:27 apanda009 阅读(154) 评论(0) 推荐(0)
160. Intersection of Two Linked Lists
摘要：第一想法是用HashSet<ListNode>, A list先遍历，存HashSet，然后B list遍历，发现ListNode存在就返回。但是这个方法不满足O(1)memory的要求。 再想了一会儿，略微受了点提醒，发现可以利用这个O(n) time做文章。这个条件方便我们scan list几次 阅读全文
posted @ 2017-08-19 18:20 apanda009 阅读(166) 评论(0) 推荐(0)
13. Roman to Integer and Integer to Roman
摘要：Leetcode 12, 13(需要考虑输入不合法的情况，比如“VV”或者“IIII”都是不合法的输入，要输出错误信息): if (s.indexOf(II) .. throw new A.... 如今我们最常见的罗马数字就是钟表的表盘符号：Ⅰ，Ⅱ，Ⅲ，Ⅳ（IIII），Ⅴ，Ⅵ，Ⅶ，Ⅷ，Ⅸ，Ⅹ，Ⅺ，Ⅻ 阅读全文
posted @ 2017-08-18 22:10 apanda009 阅读(169) 评论(0) 推荐(0)
73. Set Matrix Zeroes
摘要：这是一个矩阵操作的题目，目标很明确，就是如果矩阵如果有元素为0，就把对应的行和列上面的元素都置为0。这里最大的问题就是我们遇到0的时候不能直接把矩阵的行列在当前矩阵直接置0，否则后面还没访问到的会被当成原来是0，最后会把很多不该置0的行列都置0了。一个直接的想法是备份一个矩阵，然后在备份矩阵上判断， 阅读全文
posted @ 2017-08-16 10:44 apanda009 阅读(133) 评论(0) 推荐(0)
Find All Duplicates in an Array
摘要：根据题目的条件: 只有充分挖掘利用才行啊 键值对!!! 将值作为键, 并置为负来判断是否遍历过 阅读全文
posted @ 2017-08-08 17:56 apanda009 阅读(158) 评论(0) 推荐(0)
229. Majority Element II
摘要：Boyer-Moore Majority Vote algorithm The essential concepts is you keep a counter for the majority number X. If you find a number Y that is not X, the 阅读全文
posted @ 2017-08-07 09:08 apanda009 阅读(149) 评论(0) 推荐(0)
523. Continuous Subarray Sum
摘要：这种考subarray sum 常用到累加和数组啊, 要清楚从哪到哪开始求和, 在看题意怎么判断就ok了, 数组subarray sum 问题常常用累加和基础上改变 没想到用hashmap O(n) 即可, 关键是存的都是k的余数, 然后余数相见等于零即可 if (k != 0) runningSu 阅读全文
posted @ 2017-08-03 21:48 apanda009 阅读(273) 评论(0) 推荐(0)