Best Approach Code Although there is one approach with O(N) also

Water the Plants

class Solution{
    public:
    int min_sprinklers(int gallery[], int n)
    {
        int ans = 0;
        vector<pair<int,int>>v;
        for(int i = 0; i < n; ++ i){
            if(gallery[i] == -1)continue;
            int left = max(0,i-gallery[i]);
            int right = min(n-1,i+gallery[i]);
            v.push_back({left,right});       
        }
        sort(v.begin(),v.end());
        if(v.size() == 0)return -1;
        v.push_back({ INT_MAX, INT_MAX });
        int st = 0;
        int en = -1;
        ans = 0;
        int i = 0;
        // for(auto a:v){
        //     cout<<a.first<<" "<<a.second<<endl;
        // }
        // if(st!=0)return -1;
        while(i<v.size()){
            if(v[i].first<=st){
                en = max(en,v[i].second);
                ++i;
            }else{
                ++ans;
                st = en+1;
                if(en >= n-1)break;
                if(v[i].first>en+1){
                    break;
                }
            }
        }
        if(en<n-1)return -1;
        return ans;
    }
};


// Link:- https://practice.geeksforgeeks.org/problems/410d51d667ab93f2219b15126f001f32e8bb029e/1?page=1&difficulty[]=1&difficulty[]=2&status[]=unsolved&sortBy=submissions