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mitchellirvinmitchellirvin
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Merge branch 'main' of https://github.com/neetcode-gh/leetcode into mirvin/move-python-sols-to-dir
2 parents 1ba7c0f + 8bad0fb commit 7639cc7

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‎125-Valid-Palindrome.py

Lines changed: 13 additions & 15 deletions
Original file line numberDiff line numberDiff line change
@@ -1,19 +1,17 @@
11
class Solution:
22
def isPalindrome(self, s: str) -> bool:
3-
l, r = 0, len(s) - 1
4-
while l < r:
5-
while l < r and not self.alphanum(s[l]):
6-
l += 1
7-
while l < r and not self.alphanum(s[r]):
8-
r -= 1
9-
if s[l].lower() != s[r].lower():
3+
l = 0
4+
r = len(s)-1
5+
while l<r:
6+
if s[l].lower()==s[r].lower():
7+
l+=1
8+
r-=1
9+
continue
10+
11+
elif not (65<=ord(s[l])<=90 or 97<=ord(s[l])<=122 or 48<=ord(s[l])<=57):
12+
l+=1
13+
elif not (65<=ord(s[r])<=90 or 97<=ord(s[r])<=122 or 48<=ord(s[r])<=57):
14+
r-=1
15+
else:
1016
return False
11-
l += 1
12-
r -= 1
1317
return True
14-
15-
# Could write own alpha-numeric function
16-
def alphanum(self, c):
17-
return (ord('A') <= ord(c) <= ord('Z') or
18-
ord('a') <= ord(c) <= ord('z') or
19-
ord('0') <= ord(c) <= ord('9'))

‎261-Graph-Valid-Tree.py

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
# Problem is free on Lintcode
1+
# Problem is free on Lintcode https://www.lintcode.com/problem/178/
22
class Solution:
33
"""
44
@param n: An integer

‎csharp/1-Two-Sum.cs

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
1+
public class Solution {
2+
public int[] TwoSum(int[] nums, int target) {
3+
Dictionary<int, int> indices = new Dictionary<int, int>();
4+
5+
for (int i = 0; i < nums.Length; i++) {
6+
var diff = target - nums[i];
7+
if (indices.ContainsKey(diff)) {
8+
return new int[] {indices[diff], i};
9+
}
10+
indices[nums[i]] = i;
11+
}
12+
return null;
13+
}
14+
}
15+

‎csharp/121-Best-Time-To-Buy-and-Sell-Stock.cs

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,13 @@
1+
public class Solution {
2+
public int MaxProfit(int[] prices) {
3+
int maxProfit = 0;
4+
int minPrice = prices[0];
5+
6+
for (int i = 1; i < prices.Length; i++) {
7+
int currPrice = prices[i];
8+
minPrice = Math.Min(minPrice, currPrice);
9+
maxProfit = Math.Max(maxProfit, currPrice - minPrice);
10+
}
11+
return maxProfit;
12+
}
13+
}

‎csharp/125-Valid-Palindrome.cs

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,21 @@
1+
public class Solution {
2+
public bool IsPalindrome(string s) {
3+
int left = 0;
4+
int right = s.Length - 1;
5+
6+
while (left < right) {
7+
if (!char.IsLetterOrDigit(s[left])) {
8+
left++;
9+
} else if (!char.IsLetterOrDigit(s[right])) {
10+
right--;
11+
} else {
12+
if (char.ToLower(s[left]) != char.ToLower(s[right])) {
13+
return false;
14+
}
15+
left++;
16+
right--;
17+
}
18+
}
19+
return true;
20+
}
21+
}

‎csharp/155-Min-Stack.cs

Lines changed: 28 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,28 @@
1+
public class MinStack {
2+
private Stack<int> stack;
3+
private Stack<int> minStack;
4+
5+
public MinStack() {
6+
stack = new Stack<int>();
7+
minStack = new Stack<int>();
8+
}
9+
10+
public void Push(int val) {
11+
stack.Push(val);
12+
int min = Math.Min(val, minStack.Count != 0 ? minStack.Peek() : val);
13+
minStack.Push(min);
14+
}
15+
16+
public void Pop() {
17+
stack.Pop();
18+
minStack.Pop();
19+
}
20+
21+
public int Top() {
22+
return stack.Peek();
23+
}
24+
25+
public int GetMin() {
26+
return minStack.Peek();
27+
}
28+
}

‎csharp/167-Two-Sum-II.cs

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
public class Solution {
2+
public int[] TwoSum(int[] numbers, int target) {
3+
// Using 2 pointers. Since sorted, if l+r > target, decrease r.
4+
// Else if l+r < target, increase l. Else, result is found.
5+
int left = 0, right = numbers.Length - 1;
6+
7+
while (left < right) {
8+
int sum = numbers[left] + numbers[right];
9+
if (sum > target) {
10+
right--;
11+
} else if (sum < target) {
12+
left++;
13+
} else {
14+
return new int[] {left + 1, right + 1};
15+
}
16+
}
17+
18+
return new int[0];
19+
}
20+
}

‎csharp/20-Valid-Parentheses.cs

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
public class Solution {
2+
public bool IsValid(string s) {
3+
var stack = new Stack<char>();
4+
var pairs = new Dictionary<char, char>() {
5+
[')'] = '(',
6+
[']'] = '[',
7+
['}'] = '{'
8+
};
9+
10+
foreach (char c in s) {
11+
if (!pairs.ContainsKey(c)) {
12+
stack.Push(c);
13+
} else if (stack.Count == 0 || stack.Pop() != pairs[c]) {
14+
return false;
15+
}
16+
}
17+
18+
return stack.Count == 0;
19+
}
20+
}

‎csharp/242-Valid-Anagram.cs

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
public class Solution {
2+
public bool IsAnagram(string s, string t) {
3+
if (s.Length != t.Length) return false;
4+
if (s == t) return true;
5+
6+
Dictionary<char, int> sCounts = new Dictionary<char, int>();
7+
Dictionary<char, int> tCounts = new Dictionary<char, int>();
8+
9+
for (int i = 0; i < s.Length; i++) {
10+
sCounts[s[i]] = 1 + (sCounts.ContainsKey(s[i]) ? sCounts[s[i]] : 0);
11+
tCounts[t[i]] = 1 + (tCounts.ContainsKey(t[i]) ? tCounts[t[i]] : 0);
12+
}
13+
14+
foreach (char c in sCounts.Keys) {
15+
int tCount = tCounts.ContainsKey(c) ? tCounts[c] : 0;
16+
if (sCounts[c] != tCount) return false;
17+
}
18+
return true;
19+
}
20+
}

‎csharp/3-Longest-Substring-Without-Repeating-Characters.cs

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
public class Solution {
2+
public int LengthOfLongestSubstring(string s) {
3+
int leftPointer = 0, rightPointer = 0, maxLength = 0;
4+
HashSet<int> chars = new HashSet<int>();
5+
6+
while (rightPointer < s.Length) {
7+
char currChar = s[rightPointer];
8+
if (chars.Contains(currChar)) { // Move left pointer until all duplicate chars removed
9+
chars.Remove(s[leftPointer]);
10+
leftPointer++;
11+
} else {
12+
chars.Add(currChar);
13+
maxLength = Math.Max(maxLength, rightPointer - leftPointer + 1);
14+
rightPointer++;
15+
}
16+
}
17+
return maxLength;
18+
}
19+
}

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