feat: 3_longest_substring_without_repeating_characters

13_roman_to_integer/main.cpp

@@ -0,0 +1,49 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    int romanToInt(string s) {
+        int result = 0;
+
+        for (int i = 0; i < s.length(); i++) {
+            switch (s[i]) {
+                case 'M':
+                    result += 1000;
+                    break;
+                case 'D':
+                    result += 500;
+                    break;
+                case 'C':
+                    if (i < s.length() - 1 && (s[i + 1] == 'M' || s[i + 1] == 'D')) {
+                        result -= 100;
+                    } else {
+                        result += 100;
+                    }
+                    break;
+                case 'L':
+                    result += 50;
+                    break;
+                case 'X':
+                    if (i < s.length() - 1 && (s[i + 1] == 'C' || s[i + 1] == 'L')) {
+                        result -= 10;
+                    } else {
+                        result += 10;
+                    }
+                    break;
+                case 'V':
+                    result += 5;
+                    break;
+                case 'I':
+                    if (i < s.length() - 1 && (s[i + 1] == 'X' || s[i + 1] == 'V')) {
+                        result -= 1;
+                    } else {
+                        result += 1;
+                    }
+                    break;
+            }
+        }
+
+        return result;
+    }
+};

3_longest_substring_without_repeating_characters/main.cpp

@@ -0,0 +1,35 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        int maxLen = 0, currentLen = 0;
+        queue<int> substr;
+        unordered_set<int> charset;
+
+        for (int index = 0; index < s.length(); index++) {
+            char currentChar = s[index];
+
+            // has repeat
+            if (charset.find(currentChar) != charset.end()) {
+                while (substr.front() != currentChar) {
+                    charset.erase(substr.front());
+                    substr.pop();
+                    currentLen--;
+                }
+                charset.erase(currentChar);
+                substr.pop();
+                currentLen--;
+            }
+
+            charset.emplace(currentChar);
+            substr.emplace(currentChar);
+            currentLen++;
+
+            maxLen = max(maxLen, currentLen);
+        }
+
+        return maxLen;
+    }
+};

3_palindrome_number/main.cpp

@@ -0,0 +1,19 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    bool isPalindrome(int x) {
+        if (x < 0) return false;
+
+        string num = to_string(x);
+        int len = num.length();
+        for (int i = 0; i < len / 2; i++) {
+            if (num[i] != num[len - i - 1]) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+};