Create longest-substring-with-at-most-two-distinct-characters.cpp

Author: kamyu104

C++/longest-substring-with-at-most-two-distinct-characters.cpp

@@ -0,0 +1,26 @@
+// Time:  O(n)
+// Space: O(1)
+
+class Solution {
+public:
+    int lengthOfLongestSubstringTwoDistinct(string s) {
+        const int k = 2;
+        int longest = 0, start = 0, distinct_count = 0;
+        array<int, 256> visited = {0};
+        for (int i = 0; i < s.length(); ++i) {
+            if (visited[s[i]] == 0) {
+                ++distinct_count;
+            }
+            ++visited[s[i]];
+            while (distinct_count > k) {
+                --visited[s[start]];
+                if (visited[s[start]] == 0) {
+                    --distinct_count;
+                }
+                ++start;
+            }
+            longest = max(longest, i - start + 1);
+        }
+        return longest;
+    }
+};