Create missing-ranges.cpp

Author: kamyu104

C++/missing-ranges.cpp

@@ -0,0 +1,28 @@
+// Time:  O(n)
+// Space: O(1)
+
+class Solution {
+public:
+    vector<string> findMissingRanges(vector<int>& nums, int lower, int upper) {
+        vector<string> ranges;
+        for (int i = 0, pre = lower - 1, cur = 0; i <= nums.size(); ++i, pre = cur) {
+            if (i == nums.size()) {
+                cur = upper + 1;
+            } else {
+                cur = nums[i];
+            }
+            if (cur - pre >= 2) {
+                ranges.emplace_back(getRange(pre + 1, cur - 1));
+            }
+        }
+        return ranges;
+    }
+
+    string getRange(const int lower, const int upper) {
+        if (lower == upper) {
+            return to_string(lower);
+        } else {
+            return to_string(lower) + "->" + to_string(upper);
+        }
+    }
+};