Avoid Flood in The City
Your country has 10^9 lakes. Initially, all lakes are empty, but when it rains over the n^th lake, the n^th lake becomes full of water. If it rains over a lake that is full of water, there will be a flood. Your goal is to avoid floods in every lake.
Given an integer array rains where:
rains[i] > 0means there will be rain over lakerains[i].rains[i] == 0means there is no rain this day, and you must choose one lake this day and dry it.
Return an array ans where:
ans.length == rains.length.ans[i] == -1ifrains[i] > 0.ans[i]is the lake you choose to dry on thei^thday ifrains[i] == 0.
If there are multiple valid answers, return any of them. If it is impossible to avoid a flood, return an empty array.
Notice that if you choose to dry a full lake, it becomes empty, but if you choose to dry an empty lake, nothing changes.
Example 1
Input
rains = [1,2,3,4]Output
[-1,-1,-1,-1]There is no day to dry any lake, but each lake is rained on only once, so no flood occurs.
Example 2
Input
rains = [1,2,0,0,2,1]Output
[-1,-1,2,1,-1,-1]Drying lake 2 on the third day and lake 1 on the fourth day prevents both lakes from flooding when it rains on them again.
Constraints
- 1 <= rains.length <= 10^5
- 0 <= rains[i] <= 10^9