春节刷题day13：LeetCode
面试题 05.07. 配对交换
面试题 02.01. 移除重复节点
面试题 08.03. 魔术索引
面试题 01.02. 判定是否互为字符重排
面试题 17.04. 消失的数字
1、面试题 05.07. 配对交换
class Solution {
public:
int exchangeBits(int num) {
for(int i = 1; i < 31; i += 2){
if((num & (1 << i)) && !(num & (1 << (i - 1)))){
num ^= (1 << i); num |= (1 << (i - 1));
}
else if(!(num & (1 << i)) && (num & (1 << (i - 1)))){
num |= (1 << i); num ^= (1 << (i - 1));
}
}
return num;
}
};
2、面试题 02.01. 移除重复节点
/**
* Definition for singly-linked list.
* struct ListNode {
* int val;
* ListNode *next;
* ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* removeDuplicateNodes(ListNode* head) {
unordered_set<int> vis;
ListNode* HEAD = new ListNode(1);
if(head == NULL) return HEAD -> next;
HEAD -> next = head;
ListNode* pre = HEAD;
while(head){
ListNode* r = head -> next;
if(!vis.count(head -> val)){
vis.insert(head -> val);
pre = head; head = r;
}else{
pre -> next = r;
head = r;
}
}
return HEAD -> next;
}
};
3、面试题 08.03. 魔术索引
//这一题并没有想到分治，等明天再回来补吧
class Solution {
public:
int findMagicIndex(vector<int>& nums) {
for(int i = 0; i < nums.size(); i++)
if(nums[i] == i){
return i;
}
return -1;
}
};
4、面试题 01.02. 判定是否互为字符重排
class Solution {
public:
bool CheckPermutation(string s1, string s2) {
sort(s1.begin(), s1.end());
sort(s2.begin(), s2.end());
return s1 == s2;
}
};
class Solution {
public:
bool CheckPermutation(string s1, string s2) {
unordered_map<int, int> pa;
for(int i = 0; i < s1.size(); i++) pa[s1[i]]++;
for(int i = 0; i < s2.size(); i++) pa[s2[i]]--;
for(auto i : pa){
if(i.second != 0) return false;
}
return true;
}
};
5、面试题 17.04. 消失的数字
class Solution {
public:
int missingNumber(vector<int>& nums) {
long long sum = 0;
for(long long i = 0; i <= nums.size(); i++) sum += i;
for(int i = 0; i < nums.size(); i++) sum -= nums[i];
return (int)sum;
}
};
2021/2/18完结（年后上班第一天，太累了，完全不想动）。