leetcode难度及面试频率

 

 

 

 

 

 

 

 

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

 

Mark ！！必以努力。