## 回溯算法

| \# | 题名 | 题解 | 通过率 | 难度 | 出现频率   |
|------|----------------------|-----|--------|----|--------|
|93|[复原IP地址](https://leetcode-cn.com/problems/restore-ip-addresses)   |[77](https://leetcode-cn.com/problems/restore-ip-addresses/solution)|45.0%|中等|54.19%|
|46|[全排列](https://leetcode-cn.com/problems/permutations)   |[182](https://leetcode-cn.com/problems/permutations/solution)|73.2%|中等|50.81%|
|10|[正则表达式匹配](https://leetcode-cn.com/problems/regular-expression-matching)   |[130](https://leetcode-cn.com/problems/regular-expression-matching/solution)|25.4%|困难|44.8%|
|37|[解数独](https://leetcode-cn.com/problems/sudoku-solver)   |[63](https://leetcode-cn.com/problems/sudoku-solver/solution)|58.4%|困难|43.19%|
|411|[最短特异单词缩写](https://leetcode-cn.com/problems/minimum-unique-word-abbreviation)   |[7](https://leetcode-cn.com/problems/minimum-unique-word-abbreviation/solution)|46.8%|困难|42.15%|
|1240|[铺瓷砖](https://leetcode-cn.com/problems/tiling-a-rectangle-with-the-fewest-squares)   |[9](https://leetcode-cn.com/problems/tiling-a-rectangle-with-the-fewest-squares/solution)|44.9%|困难|40.27%|
|44|[通配符匹配](https://leetcode-cn.com/problems/wildcard-matching)   |[51](https://leetcode-cn.com/problems/wildcard-matching/solution)|25.6%|困难|38.02%|
|51|[N皇后](https://leetcode-cn.com/problems/n-queens)   |[110](https://leetcode-cn.com/problems/n-queens/solution)|67.1%|困难|36.46%|
|22|[括号生成](https://leetcode-cn.com/problems/generate-parentheses)   |[235](https://leetcode-cn.com/problems/generate-parentheses/solution)|72.6%|中等|36.06%|
|17|[电话号码的字母组合](https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number)   |[255](https://leetcode-cn.com/problems/letter-combinations-of-a-phone-number/solution)|51.7%|中等|35.71%|
|78|[子集](https://leetcode-cn.com/problems/subsets)   |[131](https://leetcode-cn.com/problems/subsets/solution)|75.7%|中等|34.02%|
|126|[单词接龙 II](https://leetcode-cn.com/problems/word-ladder-ii)   |[35](https://leetcode-cn.com/problems/word-ladder-ii/solution)|30.3%|困难|31.84%|
|79|[单词搜索](https://leetcode-cn.com/problems/word-search)   |[86](https://leetcode-cn.com/problems/word-search/solution)|39.6%|中等|31.84%|
|39|[组合总和](https://leetcode-cn.com/problems/combination-sum)   |[122](https://leetcode-cn.com/problems/combination-sum/solution)|67.6%|中等|30.78%|
|140|[单词拆分 II](https://leetcode-cn.com/problems/word-break-ii)   |[40](https://leetcode-cn.com/problems/word-break-ii/solution)|37.3%|困难|30.22%|
|306|[累加数](https://leetcode-cn.com/problems/additive-number)   |[22](https://leetcode-cn.com/problems/additive-number/solution)|31.7%|中等|27.38%|
|1087|[字母切换](https://leetcode-cn.com/problems/brace-expansion)   |[8](https://leetcode-cn.com/problems/brace-expansion/solution)|42.4%|中等|27.19%|
|212|[单词搜索 II](https://leetcode-cn.com/problems/word-search-ii)   |[29](https://leetcode-cn.com/problems/word-search-ii/solution)|38.5%|困难|27.13%|
|784|[字母大小写全排列](https://leetcode-cn.com/problems/letter-case-permutation)   |[57](https://leetcode-cn.com/problems/letter-case-permutation/solution)|61.5%|简单|26.92%|
|131|[分割回文串](https://leetcode-cn.com/problems/palindrome-partitioning)   |[45](https://leetcode-cn.com/problems/palindrome-partitioning/solution)|64.7%|中等|25.73%|
|77|[组合](https://leetcode-cn.com/problems/combinations)   |[59](https://leetcode-cn.com/problems/combinations/solution)|71.8%|中等|25.66%|
|1215|[步进数](https://leetcode-cn.com/problems/stepping-numbers)   |[12](https://leetcode-cn.com/problems/stepping-numbers/solution)|34.9%|中等|25.54%|
|996|[正方形数组的数目](https://leetcode-cn.com/problems/number-of-squareful-arrays)   |[10](https://leetcode-cn.com/problems/number-of-squareful-arrays/solution)|42.1%|困难|25.11%|
|980|[不同路径 III](https://leetcode-cn.com/problems/unique-paths-iii)   |[13](https://leetcode-cn.com/problems/unique-paths-iii/solution)|68.7%|困难|24.28%|
|216|[组合总和 III](https://leetcode-cn.com/problems/combination-sum-iii)   |[47](https://leetcode-cn.com/problems/combination-sum-iii/solution)|69.3%|中等|22.12%|
|60|[第k个排列](https://leetcode-cn.com/problems/permutation-sequence)   |[105](https://leetcode-cn.com/problems/permutation-sequence/solution)|47.6%|中等|21.71%|
|526|[优美的排列](https://leetcode-cn.com/problems/beautiful-arrangement)   |[15](https://leetcode-cn.com/problems/beautiful-arrangement/solution)|57.8%|中等|21.49%|
|294|[翻转游戏 II](https://leetcode-cn.com/problems/flip-game-ii)   |[10](https://leetcode-cn.com/problems/flip-game-ii/solution)|54.9%|中等|20.06%|
|52|[N皇后 II](https://leetcode-cn.com/problems/n-queens-ii)   |[55](https://leetcode-cn.com/problems/n-queens-ii/solution)|76.5%|困难|19.55%|
|90|[子集 II](https://leetcode-cn.com/problems/subsets-ii)   |[57](https://leetcode-cn.com/problems/subsets-ii/solution)|57.9%|中等|18.32%|
|47|[全排列 II](https://leetcode-cn.com/problems/permutations-ii)   |[85](https://leetcode-cn.com/problems/permutations-ii/solution)|56.2%|中等|17.98%|
|1219|[黄金矿工](https://leetcode-cn.com/problems/path-with-maximum-gold)   |[18](https://leetcode-cn.com/problems/path-with-maximum-gold/solution)|60.5%|中等|17.41%|
|40|[组合总和 II](https://leetcode-cn.com/problems/combination-sum-ii)   |[94](https://leetcode-cn.com/problems/combination-sum-ii/solution)|58.9%|中等|12.44%|
|842|[将数组拆分成斐波那契序列](https://leetcode-cn.com/problems/split-array-into-fibonacci-sequence)   |[20](https://leetcode-cn.com/problems/split-array-into-fibonacci-sequence/solution)|35.3%|中等|12.36%|
|1079|[活字印刷](https://leetcode-cn.com/problems/letter-tile-possibilities)   |[24](https://leetcode-cn.com/problems/letter-tile-possibilities/solution)|72.3%|中等|10.37%|
|357|[计算各个位数不同的数字个数](https://leetcode-cn.com/problems/count-numbers-with-unique-digits)   |[26](https://leetcode-cn.com/problems/count-numbers-with-unique-digits/solution)|49.0%|中等|10.3%|
|401|[二进制手表](https://leetcode-cn.com/problems/binary-watch)   |[51](https://leetcode-cn.com/problems/binary-watch/solution)|50.8%|简单|8.66%|
|89|[格雷编码](https://leetcode-cn.com/problems/gray-code)   |[56](https://leetcode-cn.com/problems/gray-code/solution)|67.0%|中等|5.84%|
|1239|[串联字符串的最大长度](https://leetcode-cn.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters)   |[39](https://leetcode-cn.com/problems/maximum-length-of-a-concatenated-string-with-unique-characters/solution)|35.8%|中等|4.28%|
|1291|[顺次数](https://leetcode-cn.com/problems/sequential-digits)   |[34](https://leetcode-cn.com/problems/sequential-digits/solution)|45.5%|中等| |
|1286|[字母组合迭代器](https://leetcode-cn.com/problems/iterator-for-combination)   |[14](https://leetcode-cn.com/problems/iterator-for-combination/solution)|53.9%|中等| |
|1258|[近义词句子](https://leetcode-cn.com/problems/synonymous-sentences)   |[19](https://leetcode-cn.com/problems/synonymous-sentences/solution)|54.4%|中等| |
|1088|[易混淆数 II](https://leetcode-cn.com/problems/confusing-number-ii)   |[7](https://leetcode-cn.com/problems/confusing-number-ii/solution)|30.9%|困难| |
|1066|[校园自行车分配 II](https://leetcode-cn.com/problems/campus-bikes-ii)   |[9](https://leetcode-cn.com/problems/campus-bikes-ii/solution)|33.1%|中等| |
|691|[贴纸拼词](https://leetcode-cn.com/problems/stickers-to-spell-word)   |[3](https://leetcode-cn.com/problems/stickers-to-spell-word/solution)|42.9%|困难| |
|425|[单词方块](https://leetcode-cn.com/problems/word-squares)   |[4](https://leetcode-cn.com/problems/word-squares/solution)|49.2%|困难| |
|351|[安卓系统手势解锁](https://leetcode-cn.com/problems/android-unlock-patterns)   |[16](https://leetcode-cn.com/problems/android-unlock-patterns/solution)|63.4%|中等| |
|320|[列举单词的全部缩写](https://leetcode-cn.com/problems/generalized-abbreviation)   |[9](https://leetcode-cn.com/problems/generalized-abbreviation/solution)|62.5%|中等| |
|291|[单词规律 II](https://leetcode-cn.com/problems/word-pattern-ii)   |[8](https://leetcode-cn.com/problems/word-pattern-ii/solution)|53.2%|困难| |
|267|[回文排列 II](https://leetcode-cn.com/problems/palindrome-permutation-ii)   |[14](https://leetcode-cn.com/problems/palindrome-permutation-ii/solution)|39.2%|中等| |
|254|[因子的组合](https://leetcode-cn.com/problems/factor-combinations)   |[12](https://leetcode-cn.com/problems/factor-combinations/solution)|55.2%|中等| |
|211|[添加与搜索单词 - 数据结构设计](https://leetcode-cn.com/problems/add-and-search-word-data-structure-design)   |[34](https://leetcode-cn.com/problems/add-and-search-word-data-structure-design/solution)|41.3%|中等| |