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‎Interview/Algorithm/Array.md‎

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10. Monotonic Array
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11. Longest Continuous Increasing Subsequence
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12. Maximum Product Subarray
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13. First Missing Positive
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14. Maximum Swap
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15. Meeting Room II
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16. Sort Colors
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## Implementation
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}
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};
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```
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### **Maximum Product Subarray**
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***Big O:*** O(n) speed, O(1) space
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return result;
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}
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};
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```
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### **First Missing Positive**
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***Big O:*** O(n) speed, O(1) space
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```
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Tips:
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Hashmap.
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```
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```c++
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class Solution {
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public:
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int firstMissingPositive(vector<int>& nums) {
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unordered_map<int, int> umap;
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int max_v = 0;
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for (int i = 0; i < nums.size(); i++) {
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if (nums[i] > 0) {
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umap[nums[i]] = 1;
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max_v = max(max_v, nums[i]);
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}
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}
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for (int i = 1; i < max_v; i++) {
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if (umap.find(i) == umap.end())
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return i;
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}
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return max_v+1;
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}
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};
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```
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### **Maximum Swap**
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***Big O:*** O(n) speed, O(1) space
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```
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Tips:
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Greedy.
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```
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```c++
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class Solution {
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public:
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int maximumSwap(int num) {
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string num_str = to_string(num);
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int n = num_str.size();
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int max_val = -1, max_i = -1;
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int left = -1, right = -1;
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for (int i = n - 1; i >= 0; i--) {
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if (num_str[i] > max_val) {
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max_val = num_str[i];
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max_i = i;
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} else if (num_str[i] < max_val) {
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left = i;
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right = max_i;
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}
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}
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if (left == -1) return num;
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char c = num_str[left];
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num_str[left] = num_str[right];
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num_str[right] = c;
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return stoi(num_str);
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}
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};
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```
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### **Meeting Rooms II**
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***Big O:*** O(nlog(n)) speed, O(n) space
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```
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Tips:
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569+
Sort + priority queue. Kick people out if their meeting is already finished.
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```
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```c++
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class Solution {
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public:
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int minMeetingRooms(vector<vector<int>>& intervals) {
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sort(intervals.begin(), intervals.end());
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priority_queue<int, vector<int>, greater<int>> pq;
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for (auto v : intervals) {
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// check if the last meetings need to be completed
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// before this meeting starts.
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if (!pq.empty() && pq.top() <= v[0]) {
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pq.pop();
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}
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// start this meeting and enter the end time.
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pq.push(v[1]);
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}
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return pq.size();
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}
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};
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```
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### **Sort Colors**
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***Big O:*** O(n) speed (one pass), O(1) space
598+
```
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Tips:
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The idea of solution is to move curr pointer along the array, if nums[curr] = 0 - swap it with nums[p0], if nums[curr] = 2 - swap it with nums[p2].
602+
```
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```c++
604+
class Solution {
605+
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public:
607+
void sortColors(vector<int>& nums) {
608+
int lo = 0, hi = nums.size() - 1, i = 0;
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while (i <= hi) {
611+
if (nums[i] == 0) swap(nums, lo++, i++);
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else if (nums[i] == 2) swap(nums, i, hi--);
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else if (nums[i] == 1) i++;
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}
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}
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void swap(vector<int>& nums, int i, int j) {
618+
int t = nums[i];
619+
nums[i] = nums[j];
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nums[j] = t;
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}
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};
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```

‎Interview/Algorithm/LeetCode_for_embedded_advanced.md‎

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18. Add Two Numbers v
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19. Add Two Numbers II v
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20. Linked List Insetion Sort v
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21. Reorder List v
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***Bit Manipulation:***
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1. Reverse Bits v
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27. Monotonic Array v
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28. Longest Continuous Increasing Subsequence v
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29. Maximum Product Subarray v
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30. First Missing Positive v
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31. Maximum Swap v
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32. Meeting Room II v
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33. Sort Colors v
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***Math:***
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1. Add Binary v
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2. Rotate a matrix by 90 degree v
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3. Sparse Matrix Multiplication
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4. Search 2D Matrix
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5. Diagonal Traverse v
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98104
***Data Structure:***
99105
1. Insert Delete GetRandom O(1) v
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1. Valid Palindrome II v
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2. Valid Palindrome v
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3. Decode String v
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4. Find All Anagrams in a String v
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### Impplementations
110117
Verifying an Alien Dictionary

‎Interview/Algorithm/linked_list.md‎

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## Linked list problems
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## Problems
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Index # | Title | Diffculty | Importance/Frequency
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----|----|----|---
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11 | LRU cache | Hard | ****
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12 | Middle of linked list | Easy | ****
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13 | Implement queue by linked list | Easy | ****
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14 | Reorder List | Medium | ****
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## Implementation
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### **Reorder List**
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***Big O:*** O(n) speed, O(1) space
25+
```
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Tips:
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1. Find a Middle Node.
29+
2. Reverse the Second Part of the List.
30+
3. Merge Two Sorted Lists.
31+
```
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```c++
33+
class Solution {
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public:
35+
void reorderList(ListNode* head) {
36+
if ( ! head ) return;
37+
ListNode *slow = head, *fast = head;
38+
while ( fast->next && fast->next->next )
39+
{
40+
slow = slow->next;
41+
fast = fast->next->next;
42+
}
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44+
45+
ListNode *prev = NULL, *cur = slow->next, *save;
46+
while ( cur )
47+
{
48+
save = cur->next;
49+
cur->next = prev;
50+
prev = cur;
51+
cur = save;
52+
}
53+
54+
slow->next = NULL;
55+
56+
ListNode *head2 = prev;
57+
while ( head2 )
58+
{
59+
save = head->next;
60+
head->next = head2;
61+
head = head2;
62+
head2 = save;
63+
}
64+
}
65+
};
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```

‎Interview/Algorithm/matrix.md‎

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## Problems
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1. Diagonal Traverse
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## Implementation
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8+
### **Diagonal Traverse**
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10+
***Big O:*** O(n*m) speed, O(min(n,m)) space
11+
```
12+
Tips:
13+
14+
```
15+
```c++
16+
class Solution {
17+
public:
18+
vector<int> findDiagonalOrder(vector<vector<int>>& matrix) {
19+
int rows = matrix.size();
20+
if (rows == 0)
21+
return vector<int>();
22+
23+
int cols = matrix[0].size();
24+
if (cols == 0)
25+
return vector<int>();
26+
27+
int dig_size = rows + cols - 1;
28+
29+
vector<int> ret;
30+
int i = 0, j = 0;
31+
for (int k = 1; k <= dig_size; k++) {
32+
vector<int> diag{};
33+
i = k >= rows ? rows-1 : k-1;
34+
j = k >= rows ? k-rows : 0;
35+
while(i >= 0 && j < cols) {
36+
diag.push_back(matrix[i][j]);
37+
i--;
38+
j++;
39+
}
40+
if (k%2 == 0)
41+
reverse(diag.begin(), diag.end());
42+
ret.insert(ret.end(), diag.begin(), diag.end());
43+
}
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return ret;
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}
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};
48+
```

‎Interview/Algorithm/string.md‎

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1. Valid Palindrome II
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2. Valid Palindrome
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3. Decode String
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3. Decode String
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4. Find All Anagrams in a String
67

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## Implementation
89

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140141
return ret;
141142
}
142143
};
144+
```
145+
### **Find All Anagrams in a String**
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***Big O:*** O(Ns + Np), O(1) space (no more than 26 characters)
148+
```
149+
Tips:
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151+
Sliding Window with HashMap or Sliding Window with Array with 26 entries
152+
```
153+
```c++
154+
class Solution {
155+
public:
156+
vector<int> findAnagrams(string s, string p) {
157+
unordered_map<char, int> p_umap, s_umap;
158+
vector<int> ret;
159+
160+
if (s.size() < p.size())
161+
return ret;
162+
163+
for (auto c : p)
164+
p_umap[c] ++;
165+
166+
int st = 0, end = 0;
167+
168+
while (end < s.size()) {
169+
//cout << st << end << endl;
170+
if (end-st+1 < p.size()) {
171+
if (p_umap.find(s[end]) != p_umap.end()) {
172+
s_umap[s[end]] ++;
173+
end ++;
174+
} else {
175+
s_umap.clear();
176+
end ++;
177+
st = end;
178+
}
179+
} else if ((end-st+1 > p.size())) {
180+
if (s_umap[s[st]] == 1)
181+
s_umap.erase(s[st]);
182+
else
183+
s_umap[s[st]] --;
184+
st ++;
185+
} else {
186+
s_umap[s[end]] ++;
187+
if (s_umap == p_umap)
188+
ret.push_back(st);
189+
end ++;
190+
}
191+
}
192+
193+
return ret;
194+
}
195+
};
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```

‎README.md‎

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## Interview Questions
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307307
### [A. LeetCode Questions for Embedded Developers](Interview/Algorithm/LeetCode_for_Embedded_Developer.md)
308-
1. Bitwise Operations
308+
1. [Advanced Leetcode Questions](Interview/Algorithm/LeetCode_for_embedded_advanced.md)
309309
2. [Linked list](Interview/Algorithm/linked_list.md)
310-
3. String
311-
4. Array
312-
5. Math
310+
3. [String]((Interview/Algorithm/string.md))
311+
4. [Array](Interview/Algorithm/Array.md)
312+
5. [Math](Interview/Algorithm/math.md)
313+
6. [Data Structure](Interview/Algorithm/dataStructure.md)
313314

314315
### B. Other Algorithms Questions
315316
1. Sliding Window

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