Create avoid-flood-in-the-city.cpp

Author: kamyu104

C++/avoid-flood-in-the-city.cpp

@@ -0,0 +1,32 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    vector<int> avoidFlood(vector<int>& rains) {
+        unordered_map<int, vector<int>> lookup;
+        for (int i = rains.size() - 1; i >= 0; --i) {
+            lookup[rains[i]].emplace_back(i);
+        }
+        vector<int> result;
+        priority_queue<int, vector<int>, greater<int>> min_heap;
+        for (int i = 0; i < rains.size(); ++i) {
+            if (rains[i]) {
+                if (lookup[rains[i]].size() >= 2) {
+                    lookup[rains[i]].pop_back();
+                    min_heap.emplace(lookup[rains[i]].back());
+                }
+                result.emplace_back(-1);
+            } else if (!min_heap.empty()) {
+                int j = min_heap.top(); min_heap.pop();
+                if (j < i) {
+                    return {};
+                }
+                result.emplace_back(rains[j]);
+            } else {
+                result.emplace_back(1);
+            }
+        }
+        return min_heap.empty() ? result : vector<int>();
+    }
+};