Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.
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class Solution { public: bool containsDuplicate(vector<int>& nums) { set<int> m; for(int i = 0; i < nums.size(); i++) { m.insert(nums[i]); } return nums.size() != m.size(); } }; |
Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.
You may assume that the array is non-empty and the majority element always exist in the array.
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class Solution { public: int majorityElement(vector<int>& nums) { sort(nums.begin(), nums.end()); int temp = 0, maxvalue = 0, ans = nums[0]; for(int i = 1; i < nums.size(); i++) { if(nums[i - 1] == nums[i]) { temp++; if(temp > maxvalue) { maxvalue = temp; ans = nums[i]; } } else { temp = 0; } } return ans; } }; |
Related to question Excel Sheet Column Title
Given a column title as appear in an Excel sheet, return its corresponding column number.
For example:
A -> 1
B -> 2
C -> 3
…
Z -> 26
AA -> 27
AB -> 28
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class Solution { public: int titleToNumber(string s) { int ans = 0; for(int i = 0; i < s.length(); i++) { ans = ans*26 + s[i] - 'A' + 1; } return ans; } }; |
Given two strings s and t, write a function to determine if t is an anagram of s.
For example,
s = “anagram”, t = “nagaram”, return true.
s = “rat”, t = “car”, return false.
Note:
You may assume the string contains only lowercase alphabets.
Follow up:
What if the inputs contain unicode characters? How would you adapt your solution to such case?
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class Solution { public: bool isAnagram(string s, string t) { int a[26] = {0}; if(s.length() != t.length()) return 0; for(int i = 0; i < s.length(); i++) { a[s[i] - 'a']++; } for(int i = 0; i < t.length(); i++) { a[t[i] -'a']--; } for(int i = 0; i < 26; i++) { if(a[i] != 0) { return 0; } } return 1; } }; |
Given two binary trees, write a function to check if they are equal or not.
Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
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/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: bool isSameTree(TreeNode* p, TreeNode* q) { if(p != NULL && q != NULL) return p->val == q->val && isSameTree(p->left, q->left) && isSameTree(p->right, q->right); return p == NULL && q == NULL; } }; |
237. Delete Node in a Linked List
Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.
Supposed the linked list is 1 -> 2 -> 3 -> 4 and you are given the third node with value 3, the linked list should become 1 -> 2 -> 4 after calling your function.
分析：因为删除结点本来的步骤是找到当前结点的前一个结点，然后修改前一个结点的 next 指针指向。现在只知道当前要删除的结点，而不知道要删除结点的前一个结点，所以可以通过修改当前要删除结点的值，然后将当前结点指针指向 next 的 next （也就是变成了把后一个结点的值赋给当前结点，然后删除要删除结点的下一个结点），达到删除结点的目的～
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class Solution { public: void deleteNode(ListNode* node) { node->val = node->next->val; node->next = node->next->next; } }; |