Given an array of integers, return indices of the two numbers such that they add up to a specific target.
3 |You may assume that each input would have exactly one solution, and you may not use the same element twice.
4 |Example:
5 |Given nums = [2, 7, 11, 15], target = 9, 6 | 7 | Because nums[0] + nums[1] = 2 + 7 = 9, 8 | return [0, 1]. 9 |10 |
Given a 32-bit signed integer, reverse digits of an integer.
12 |Example 1:
13 |Input: 123 14 | Output: 321 15 |16 |
Example 2:
17 |Input: -123 18 | Output: -321 19 |20 |
Example 3:
21 |Input: 120 22 | Output: 21 23 |24 |
Note:
25 | Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231, 231 − 1]. For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
Determine whether an integer is a palindrome. An integer is a palindrome when it reads the same backward as forward.
28 |Example 1:
29 |Input: 121 30 | Output: true 31 |32 |
Example 2:
33 |Input: -121 34 | Output: false 35 | Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome. 36 |37 |
Example 3:
38 |Input: 10 39 | Output: false 40 | Explanation: Reads 01 from right to left. Therefore it is not a palindrome. 41 |42 |
Follow up:
43 |Coud you solve it without converting the integer to a string?
44 |Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
Symbol Value 47 | I 1 48 | V 5 49 | X 10 50 | L 50 51 | C 100 52 | D 500 53 | M 100054 |
For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.
Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:
I can be placed before V (5) and X (10) to make 4 and 9. X can be placed before L (50) and C (100) to make 40 and 90. C can be placed before D (500) and M (1000) to make 400 and 900.Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
62 |Example 1:
63 |Input: "III" 64 | Output: 365 |
Example 2:
66 |Input: "IV" 67 | Output: 468 |
Example 3:
69 |Input: "IX" 70 | Output: 971 |
Example 4:
72 |Input: "LVIII" 73 | Output: 58 74 | Explanation: L = 50, V= 5, III = 3. 75 |76 |
Example 5:
77 |Input: "MCMXCIV" 78 | Output: 1994 79 | Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.80 |
Write a function to find the longest common prefix string amongst an array of strings.
82 |If there is no common prefix, return an empty string "".
Example 1:
84 |Input: ["flower","flow","flight"] 85 | Output: "fl" 86 |87 |
Example 2:
88 |Input: ["dog","racecar","car"] 89 | Output: "" 90 | Explanation: There is no common prefix among the input strings. 91 |92 |
Note:
93 |All given inputs are in lowercase letters a-z.
Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
An input string is valid if:
97 |Note that an empty string is also considered valid.
102 |Example 1:
103 |Input: "()" 104 | Output: true 105 |106 |
Example 2:
107 |Input: "()[]{}"
108 | Output: true
109 |
110 | Example 3:
111 |Input: "(]" 112 | Output: false 113 |114 |
Example 4:
115 |Input: "([)]" 116 | Output: false 117 |118 |
Example 5:
119 |Input: "{[]}"
120 | Output: true
121 |
122 | Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
124 |Example: 125 |
Input: 1->2->4, 1->3->4 126 | Output: 1->1->2->3->4->4 127 |128 |
Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length.
130 |Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.
131 |Example 1:
132 |Given nums = [1,1,2], 133 | 134 | Your function should return length =137 |2, with the first two elements ofnumsbeing1and2respectively. 135 | 136 | It doesn't matter what you leave beyond the returned length.
Example 2:
138 |Given nums = [0,0,1,1,1,2,2,3,3,4], 139 | 140 | Your function should return length =144 |5, with the first five elements ofnumsbeing modified to0,1,2,3, and4respectively. 141 | 142 | It doesn't matter what values are set beyond the returned length. 143 |
Clarification:
145 |Confused why the returned value is an integer but your answer is an array?
146 |Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.
147 |Internally you can think of this:
148 |// nums is passed in by reference. (i.e., without making a copy)
149 | int len = removeDuplicates(nums);
150 |
151 | // any modification to nums in your function would be known by the caller.
152 | // using the length returned by your function, it prints the first len elements.
153 | for (int i = 0; i < len; i++) {
154 | print(nums[i]);
155 | }
156 | Given an array nums and a value val, remove all instances of that value in-place and return the new length.
158 |Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.
159 |The order of elements can be changed. It doesn't matter what you leave beyond the new length.
160 |Example 1:
161 |Given nums = [3,2,2,3], val = 3, 162 | 163 | Your function should return length = 2, with the first two elements of nums being 2. 164 | 165 | It doesn't matter what you leave beyond the returned length. 166 |167 |
Example 2:
168 |Given nums = [0,1,2,2,3,0,4,2], val = 2, 169 | 170 | Your function should return length =175 |5, with the first five elements ofnumscontaining0,1,3,0, and 4. 171 | 172 | Note that the order of those five elements can be arbitrary. 173 | 174 | It doesn't matter what values are set beyond the returned length.
Clarification:
176 |Confused why the returned value is an integer but your answer is an array?
177 |Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.
178 |Internally you can think of this:
179 |// nums is passed in by reference. (i.e., without making a copy)
180 | int len = removeElement(nums, val);
181 |
182 | // any modification to nums in your function would be known by the caller.
183 | // using the length returned by your function, it prints the first len elements.
184 | for (int i = 0; i < len; i++) {
185 | print(nums[i]);
186 | }
187 | Implement strStr().
189 |Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.
190 |Example 1:
191 |Input: haystack = "hello", needle = "ll" 192 | Output: 2 193 |194 |
Example 2:
195 |Input: haystack = "aaaaa", needle = "bba" 196 | Output: -1 197 |198 |
Clarification:
199 |What should we return when needle is an empty string? This is a great question to ask during an interview.
For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().