摘要：Given two strings s and t which consist of only lowercase letters. String t is generated by random shuffling string s and then add one more letter at 阅读全文

摘要：Problem: Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. For example: Given num = 38, the process 阅读全文

摘要：Problem： Given a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the f 阅读全文

摘要：最原始的方法：先排序，然后从头查找。若nums[i] = nums[i] + 1则为一对相同的数，i = i + 2,继续判断。若nums[i] != nums[i] + 1，则输出nums[i]。需注意不要越界！ 通过参考别人的解题报告发现，可以使用异或运算：对所有元素做异或运算，其结果为那个出现 阅读全文

摘要：此题为技巧题,需知道Nim Game的Wining Strange，即在自己的局中，如果剩余数目为4的倍数，则不可能取胜。因此检测N是否为4的倍数即可。Background参见http://www.cdf.toronto.edu/~ajr/270/probsess/03/strategy.html 阅读全文