resot严选题
题单介绍
这个题单收录了我刷cf时遇到的一些典题，感觉这些题都很值得一做，以此记录一下
另外虽然我在表格标出了难度，但是我个人不推荐以难度为标准做题，很多题的难度都只是虚高，建议忽略难度全部都当普及-的做
| 编号 | 题目名称 | 题目链接 | 主要算法 | 难度 |
| ---- | -------------------------- | ------------------------------------------------ | ------------------- | ---- |
| 1 | E. Best Pair | https://codeforces.com/problemset/problem/1637/E | 思维 | 2100 |
| 2 | G. Three Occurrences | https://codeforces.com/problemset/problem/1418/G | 异或哈希 | 2500 |
| 3 | E. Cosmic Rays | https://codeforces.com/contest/2002/problem/E | 单调栈 | 2300 |
| 4 | B. Alyona and a tree | https://codeforces.com/problemset/problem/739/B | 树上差分+倍增 | 1900 |
| 5 | D. Cow and Fields | https://codeforces.com/problemset/problem/1307/D | 最短路 | 1900 |
| 6 | C. Xor Tree | https://codeforces.com/problemset/problem/1446/C | 字典树dp | 2100 |
| 7 | F. Xor-Paths | https://codeforces.com/problemset/problem/1006/F | 折半搜索 | 2100 |
| 8 | D. For Gamers. By Gamers. | https://codeforces.com/contest/1657/problem/D | 二分 | 2000 |
| 9 | E. Collapsing Strings | https://codeforces.com/contest/1902/problem/E | 字典树 | 1900 |
| 10 | D. XORificator | https://codeforces.com/contest/1977/problem/D | 异或哈希 | 2300 |
| 11 | D. Robot Queries | https://codeforces.com/contest/1902/problem/D | 思维+二分 | 1900 |
| 12 | D. Cut | https://codeforces.com/contest/1516/problem/D | 倍增 | 2100 |
| 13 | D. Permutation Graph | https://codeforces.com/contest/1696/problem/D | st表+分治 | 1900 |
| 14 | C. Wish I Knew How to Sort | https://codeforces.com/problemset/problem/1753/C | 期望dp | 2000 |
| 15 | D. Tree XOR | https://codeforces.com/contest/1882/problem/D | 换根dp | 1900 |
| 16 | E. Count Paths | https://codeforces.com/contest/1923/problem/E | 启发式合并 | 2000 |
| 17 | D2. 388535 (Hard Version) | https://codeforces.com/contest/1658/problem/D2 | 01字典树 | 2300 |
| 18 | F. SUM and REPLACE | https://codeforces.com/contest/920/problem/F | 势能线段树+积性函数 | 2000 |
| 19 | F. Replace on Segment | https://codeforces.com/contest/1922/problem/F | 区间dp | 2500 |
| 20 | F. Sum of Progression | https://codeforces.com/contest/1921/problem/F | 根号分治 | 1900 |
| 21 | E. Clearing Up | https://codeforces.com/contest/141/problem/E | 思维+图论 | 2300 |
| 22 | D. GCD Counting | https://codeforces.com/problemset/problem/1101/D | dp | 2000 |
| 23 | C. Cloud Computing | https://codeforces.com/problemset/problem/1070/C | 扫描线+权值线段树 | 2000 |
| 24 | E. Tufurama | https://codeforces.com/contest/961/problem/E | 数据结构 | 1900 |
| 25 | E. Generate a String | https://codeforces.com/contest/710/problem/E | dp | 2000 |
| 26 | B. Kay and Snowflake | https://codeforces.com/contest/685/problem/B | 树的重心 | 1900 |
| 27 | E. Vasya and a Tree | https://codeforces.com/problemset/problem/1076/E | 树上差分 | 1900 |
| 28 | E. Array Queries | https://codeforces.com/contest/797/problem/E | 根号分治 | 2000 |
| 29 | D. Zigzags | https://codeforces.com/contest/1400/problem/D | 枚举 | 1900 |