Q57 Avoid Flood in The City - LeetCode

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Wed Feb 01 2023 06:15:44 GMT+0000 (Coordinated Universal Time)

Saved by @Ayush_dabas07

class Solution {
    public int[] avoidFlood(int[] rains) {
        //make a treeset to store if drying 0's indexes , HM to store lakes and their idx
        HashMap<Integer,Integer> lakes = new HashMap<>();
        TreeSet<Integer> set = new TreeSet<>();
        
        int ans[] = new int[rains.length]; 

        //iterate through the rains array
        for(int i =0 ; i< rains.length ; i++){
            int val = rains[i];

            //store all 0's indexes
            if(val == 0 ){
                set.add(i);
                ans[i] = 1;         //assigning random value
            }

            else if(lakes.containsKey(val)){   // if lake already exists it needs drying
                //assumed the lake has already been dried when it comes a 2nd time,
                //therefore we have to store -1 like it has come for the first time
                ans[i] = -1;   
                
                //get index of a 0 which is higher than index of rain, as we cant replace
                // with a 0 which has occured before the lake
                Integer idx = set.higher(lakes.get(val));

                if(idx == null) //if no such 0 exists it will be flooded
                return new int[0];

                set.remove(idx);

                ans[idx] = val;
                //update the index of lake,as we to treat the new lake likes its the 1st
                //time coming
                lakes.put(val ,i);      

            }    
            
            //if lake is coming for the first time just add it to set
            else if(lakes.containsKey(val) == false){       
                ans[i] = -1;
                lakes.put(val,i);
            }
            
        }

        return ans;
    }
}

https://leetcode.com/problems/avoid-flood-in-the-city/

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