Schedule Dry Days to Prevent Any Lake Flood

### Problem Lakes 1..1000000000 start empty. A positive rains[i] fills that lake; rain on an already full lake causes a flood. On a zero day,you must choose one lake to dry; drying an empty lake is allowed. Return a same-length plan with -1 on rainy days and the chosen lake number on dry days. Any flood-free plan is accepted; return an empty array if none exists. ```cpp class Solution { public: vector<int> avoidFlood(vector<int>& rains); }; ``` ### Examples **Example 1:** ```text Input: rains = [3,0,3] Output: [-1,3,-1] Explanation: Dry lake3 between its two rains. ``` **Example 2:** ```text Input: rains = [4,4] Output: [] Explanation: The second consecutive rain floods lake4,and no dry day is available. ``` ### Constraints - rains has length 1 to 100000. - `0 <= rains[i] <= 1000000000`; positive values identify lakes,and 0 identifies a dry day. ### Contract considerations The returned lake choices are genuinely non-unique; for rains[0],drying lake 1 or lake 2 are both valid. ```hint Read the boundary condition Check repeated rain on one lake and the timing of each assigned dry day. Unused drying capacity may name an empty lake, and different valid plans remain acceptable. ``` ### What a Strong Answer Covers The returned lake choices are genuinely non-unique; for rains[0],drying lake 1 or lake 2 are both valid. ### Follow-up Questions Optional practice extension,separate from the original task: How would a limit on which lakes each dry day may drain change the scheduling problem?