Create check-if-all-the-integers-in-a-range-are-covered.cpp

Author: kamyu104

C++/check-if-all-the-integers-in-a-range-are-covered.cpp

@@ -0,0 +1,60 @@
+// Time:  O(n + r)
+// Space: O(r)
+
+// if r is small, this is better
+class Solution {
+public:
+    bool isCovered(vector<vector<int>>& ranges, int left, int right) {
+        static const int RANGE_SIZE = 50;
+
+        vector<int> interval(RANGE_SIZE + 1);
+        for (const auto& r : ranges) {
+            ++interval[r[0] - 1];
+            --interval[(r[1] - 1) + 1];
+        }
+        for (int i = 0, cnt = 0; i <= right - 1; ++i) {
+            cnt += interval[i];
+            if (i >= left - 1 && !cnt) {
+                return false;
+            }
+        }
+        return true;
+    }
+};
+
+// Time:  O(nlogn)
+// Space: O(1)
+// if r is big, this is better
+class Solution2 {
+public:
+    bool isCovered(vector<vector<int>>& ranges, int left, int right) {
+        sort(begin(ranges), end(ranges));
+        for (const auto& r : ranges) {
+            if (r[0] <= left && left <= r[1]) {
+                left = r[1] + 1;
+            }
+        }
+        return left > right;
+    }
+};
+
+// Time:  O(n * r)
+// Space: O(1)
+class Solution3 {
+public:
+    bool isCovered(vector<vector<int>>& ranges, int left, int right) {
+        for (int i = left; i <= right; ++i) {
+            bool found = false;
+            for (const auto& r : ranges) {
+                if (r[0] <= i && i <= r[1]) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) {
+                return false;
+            }
+        }
+        return true;
+    }
+};