leetcode难度及面试频率
转载自:LeetCode Question Difficulty Distribution
1 | Two Sum | 2 | 5 | array | sort | |
set | Two Pointers | |||||
2 | Add Two Numbers | 3 | 4 | linked list | Two Pointers | |
Math | ||||||
3 | Longest Substring Without Repeating Characters | 3 | 2 | string | Two Pointers | |
hashtable | ||||||
4 | Median of Two Sorted Arrays | 5 | 3 | array | Binary Search | |
5 | Longest Palindromic Substring | 4 | 2 | string | ||
6 | ZigZag Conversion | 3 | 1 | string | ||
7 | Reverse Integer | 2 | 3 | Math | ||
8 | String to Integer (atoi) | 2 | 5 | string | Math | |
9 | Palindrome Number | 2 | 2 | Math | ||
10 | Regular Expression Matching | 5 | 3 | string | Recursion | |
DP | ||||||
11 | Container With Most Water | 3 | 2 | array | Two Pointers | |
12 | Integer to Roman | 3 | 4 | Math | ||
13 | Roman to Integer | 2 | 4 | Math | ||
14 | Longest Common Prefix | 2 | 1 | string | ||
15 | 3Sum | 3 | 5 | array | Two Pointers | |
16 | 3Sum Closest | 3 | 1 | array | Two Pointers | |
17 | Letter Combinations of a Phone Number | 3 | 3 | string | DFS | |
18 | 4Sum | 3 | 2 | array | ||
19 | Remove Nth Node From End of List | 2 | 3 | linked list | Two Pointers | |
20 | Valid Parentheses | 2 | 5 | string | Stack | |
21 | Merge Two Sorted Lists | 2 | 5 | linked list | sort | |
Two Pointers | ||||||
merge | ||||||
22 | Generate Parentheses | 3 | 4 | string | DFS | |
23 | Merge k Sorted Lists | 3 | 4 | linked list | sort | |
heap | Two Pointers | |||||
merge | ||||||
24 | Swap Nodes in Pairs | 2 | 4 | linked list | ||
25 | Reverse Nodes in k-Group | 4 | 2 | linked list | Recursion | |
Two Pointers | ||||||
26 | Remove Duplicates from Sorted Array | 1 | 3 | array | Two Pointers | |
27 | Remove Element | 1 | 4 | array | Two Pointers | |
28 | Implement strStr() | 4 | 5 | string | Two Pointers | |
KMP | ||||||
rolling hash | ||||||
29 | Divide Two Integers | 4 | 3 | Binary Search | ||
Math | ||||||
30 | Substring with Concatenation of All Words | 3 | 1 | string | Two Pointers | |
31 | Next Permutation | 5 | 2 | array | permutation | |
32 | Longest Valid Parentheses | 4 | 1 | string | DP | |
33 | Search in Rotated Sorted Array | 4 | 3 | array | Binary Search | |
34 | Search for a Range | 4 | 3 | array | Binary Search | |
35 | Search Insert Position | 2 | 2 | array | ||
36 | Valid Sudoku | 2 | 2 | array | ||
37 | Sudoku Solver | 4 | 2 | array | DFS | |
38 | Count and Say | 2 | 2 | string | Two Pointers | |
39 | Combination Sum | 3 | 3 | array | combination | |
40 | Combination Sum II | 4 | 2 | array | combination | |
41 | First Missing Positive | 5 | 2 | array | sort | |
42 | Trapping Rain Water | 4 | 2 | array | Two Pointers | |
Stack | ||||||
43 | Multiply Strings | 4 | 3 | string | Two Pointers | |
Math | ||||||
44 | Wildcard Matching | 5 | 3 | string | Recursion | |
DP | ||||||
greedy | ||||||
45 | Jump Game II | 4 | 2 | array | ||
46 | Permutations | 3 | 4 | array | permutation | |
47 | Permutations II | 4 | 2 | array | permutation | |
48 | Rotate Image | 4 | 2 | array | ||
49 | Anagrams | 3 | 4 | string | ||
hashtable | ||||||
50 | Pow(x, n) | 3 | 5 | Binary Search | ||
Math | ||||||
51 | N-Queens | 4 | 3 | array | DFS | |
52 | N-Queens II | 4 | 3 | array | DFS | |
53 | Maximum Subarray | 3 | 3 | array | DP | |
54 | Spiral Matrix | 4 | 2 | array | ||
55 | Jump Game | 3 | 2 | array | ||
56 | Merge Intervals | 4 | 5 | array | sort | |
linked list | merge | |||||
red-black tree | ||||||
57 | Insert Interval | 4 | 5 | array | sort | |
linked list | merge | |||||
red-black tree | ||||||
58 | Length of Last Word | 1 | 1 | string | ||
59 | Spiral Matrix II | 3 | 2 | array | ||
60 | Permutation Sequence | 5 | 1 | permutation | ||
Math | ||||||
61 | Rotate List | 3 | 2 | linked list | Two Pointers | |
62 | Unique Paths | 2 | 3 | array | DP | |
63 | Unique Paths II | 3 | 3 | array | DP | |
64 | Minimum Path Sum | 3 | 3 | array | DP | |
65 | Valid Number | 2 | 5 | string | Math | |
66 | Plus One | 1 | 2 | array | Math | |
67 | Add Binary | 2 | 4 | string | Two Pointers | |
Math | ||||||
68 | Text Justification | 4 | 2 | string | ||
69 | Sqrt(x) | 4 | 4 | Binary Search | ||
70 | Climbing Stairs | 2 | 5 | DP | ||
71 | Simplify Path | 3 | 1 | string | Stack | |
72 | Edit Distance | 4 | 3 | string | DP | |
73 | Set Matrix Zeroes | 3 | 5 | array | ||
74 | Search a 2D Matrix | 3 | 3 | array | Binary Search | |
75 | Sort Colors | 4 | 2 | array | sort | |
Two Pointers | ||||||
76 | Minimum Window Substring | 4 | 2 | string | Two Pointers | |
77 | Combinations | 3 | 4 | combination | ||
78 | Subsets | 3 | 4 | array | Recursion | |
combination | ||||||
79 | Word Search | 3 | 4 | array | DFS | |
80 | Remove Duplicates from Sorted Array II | 2 | 2 | array | Two Pointers | |
81 | Search in Rotated Sorted Array II | 5 | 3 | array | Binary Search | |
82 | Remove Duplicates from Sorted List II | 3 | 3 | linked list | Recursion | |
Two Pointers | ||||||
83 | Remove Duplicates from Sorted List | 1 | 3 | linked list | ||
84 | Largest Rectangle in Histogram | 5 | 2 | array | Stack | |
85 | Maximal Rectangle | 5 | 1 | array | DP | |
Stack | ||||||
86 | Partition List | 3 | 3 | linked list | Two Pointers | |
87 | Scramble String | 5 | 2 | string | Recursion | |
DP | ||||||
88 | Merge Sorted Array | 2 | 5 | array | Two Pointers | |
merge | ||||||
89 | Gray Code | 4 | 2 | combination | ||
90 | Subsets II | 4 | 2 | array | Recursion | |
combination | ||||||
91 | Decode Ways | 3 | 4 | string | Recursion | |
DP | ||||||
92 | Reverse Linked List II | 3 | 2 | linked list | Two Pointers | |
93 | Restore IP Addresses | 3 | 3 | string | DFS | |
94 | Binary Tree Inorder Traversal | 4 | 3 | tree | Recursion | |
hashtable | morris | |||||
Stack | ||||||
95 | Unique Binary Search Trees II | 4 | 1 | tree | DP | |
DFS | ||||||
96 | Unique Binary Search Trees | 3 | 1 | tree | DP | |
97 | Interleaving String | 5 | 2 | string | Recursion | |
DP | ||||||
98 | Validate Binary Search Tree | 3 | 5 | tree | DFS | |
99 | Recover Binary Search Tree | 4 | 2 | tree | DFS | |
100 | Same Tree | 1 | 1 | tree | DFS | |
101 | Symmetric Tree | 1 | 2 | tree | DFS | |
102 | Binary Tree Level Order Traversal | 3 | 4 | tree | BFS | |
103 | Binary Tree Zigzag Level Order Traversal | 4 | 3 | queue | BFS | |
tree | Stack | |||||
104 | Maximum Depth of Binary Tree | 1 | 1 | tree | DFS | |
105 | Construct Binary Tree from Preorder and Inorder Tr | 3 | 3 | array | DFS | |
tree | ||||||
106 | Construct Binary Tree from Inorder and Postorder T | 3 | 3 | array | DFS | |
tree | ||||||
107 | Binary Tree Level Order Traversal II | 3 | 1 | tree | BFS | |
108 | Convert Sorted Array to Binary Search Tree | 2 | 3 | tree | DFS | |
109 | Convert Sorted List to Binary Search Tree | 4 | 3 | linked list | Recursion | |
Two Pointers | ||||||
110 | Balanced Binary Tree | 1 | 2 | tree | DFS | |
111 | Minimum Depth of Binary Tree | 1 | 1 | tree | DFS | |
112 | Path Sum | 1 | 3 | tree | DFS | |
113 | Path Sum II | 2 | 2 | tree | DFS | |
114 | Flatten Binary Tree to Linked List | 3 | 3 | tree | Recursion | |
Stack | ||||||
115 | Distinct Subsequences | 4 | 2 | string | DP | |
116 | Populating Next Right Pointers in Each Node | 3 | 3 | tree | DFS | |
117 | Populating Next Right Pointers in Each Node II | 4 | 2 | tree | DFS | |
118 | Pascal's Triangle | 2 | 1 | array | ||
119 | Pascal's Triangle II | 2 | 1 | array | ||
120 | Triangle | 3 | 1 | array | DP | |
121 | Best Time to Buy and Sell Stock | 2 | 1 | array | DP | |
122 | Best Time to Buy and Sell Stock II | 3 | 1 | array | greedy | |
123 | Best Time to Buy and Sell Stock III | 4 | 1 | array | DP | |
124 | Binary Tree Maximum Path Sum | 4 | 2 | tree | DFS | |
125 | Valid Palindrome | 2 | 5 | string | Two Pointers | |
126 | Word Ladder II | 1 | 1 | |||
127 | Word Ladder | 3 | 5 | graph | BFS | |
shortest path | ||||||
128 | Longest Consecutive Sequence | 4 | 3 | array | ||
129 | Sum Root to Leaf Numbers | 2 | 4 | tree | DFS | |
130 | Surrounded Regions | 4 | 3 | array | BFS | |
DFS | ||||||
131 | Palindrome Partitioning | 3 | 4 | string | DFS | |
132 | Palindrome Partitioning II | 4 | 3 | string | DP |