pengyu2003

摘要： Sort a linked list inO(nlogn) time using constant space complexity.逻辑正确，尾指针没有置空，调了好久……/** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */class Solution {public: ListNode *sortList(ListNode *head) {... 阅读全文

摘要： Evaluate the value of an arithmetic expression inReverse Polish Notation.Valid operators are+,-,*,/. Each operand may be an integer or another expression.Some examples: ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "13&qu 阅读全文

摘要： Given an input string, reverse the string word by word.For example,Given s = "the sky is blue",return "blue is sky the".click to show clarification.Clarification:What constitutes a word?A sequence of non-space characters constitutes a word.Could the input string contain leading o 阅读全文

摘要： Implementint sqrt(int x).Compute and return the square root ofx.此题看着简单，实则坑爹啊！！！！！首先，关于平方，int是不够用的。其次，二分法肯定好用，但是，最终的结果怎么取？原则上取小于等于的最近整数。但是mid的计算可能会更改这个数，所以需要调整一下。class Solution {public: int sqrt(int x) { long long left = 0; long long right = x; long long mid = left + (right - lef... 阅读全文

摘要： Given a collection of numbers that might contain duplicates, return all possible unique permutations.For example,[1,1,2]have the following unique permutations:[1,1,2],[1,2,1], and[2,1,1].class Solution {public: vector > re; vector > permuteUnique(vector &num) { map m; int size = ... 阅读全文