Create check-if-a-string-contains-all-binary-codes-of-size-k.cpp

Author: kamyu104

C++/check-if-a-string-contains-all-binary-codes-of-size-k.cpp

@@ -0,0 +1,39 @@
+// Time:  O(n * k)
+// Space: O(2^k)
+
+class Solution {
+public:
+    bool hasAllCodes(string s, int k) {
+        unordered_set<int> lookup;
+        const int base = 1 << k;
+        if (base > s.length()) {
+            return false;
+        }
+        int num = 0;
+        for (int i = 0; i < s.length(); ++i) {
+            num = (num << 1) + (s[i] - '0');
+            if (i >= k - 1) {
+                lookup.emplace(num);
+                num -= (s[i - k + 1] - '0') * (base >> 1);
+            }
+        }
+        return lookup.size() == base;
+    }
+};
+
+// Time:  O(n * k)
+// Space: O(k * 2^k)
+class Solution2 {
+public:
+    bool hasAllCodes(string s, int k) {
+        unordered_set<string> lookup;
+        const int base = 1 << k;
+        if (base > s.length()) {
+            return false;
+        }
+        for (int i = 0; i + k - 1 < s.length(); ++i) {
+            lookup.emplace(s.substr(i, k));
+        }
+        return lookup.size() == base;
+    }
+};