Example 1:
Input: flowerbed = [1,0,0,0,1], n = 1
Output: True
Example 2:
Input: flowerbed = [1,0,0,0,1], n = 2
Output: False
Note:
The input array won't violate no-adjacent-flowers rule.
The input array size is in the range of [1, 20000].
n is a non-negative integer which won't exceed the input array size.

class Solution {
public:
    bool canPlaceFlowers(vector<int>& flowerbed, int n) {
        flowerbed.push_back(0);
        flowerbed.push_back(1);
        int total=0;
        int start=-2;
        for(int i=0; i<flowerbed.size();i++ )
        {
            if(flowerbed[i] ) {
                int r=i-start-3;
                 start=i;
            //    cout<<r<<endl;
                if(r<1 ) continue;
​
                total += (r+ r%2) /2;
​
            } 
        }
      //  cout<<total<<endl;
        return total>=n;
    }
};