605. Can Place Flowers

Suppose you have a long flowerbed in which some of the plots are planted and some are not. However, flowers cannot be planted in adjacent plots - they would compete for water and both would die.

Given a flowerbed (represented as an array containing 0 and 1, where 0 means empty and 1 means not empty), and a number n, return if n new flowers can be planted in it without violating the no-adjacent-flowers rule.

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:

1. The input array won't violate no-adjacent-flowers rule.
2. The input array size is in the range of [1, 20000].
3. n is a non-negative integer which won't exceed the input array size.

A:

             -------------就是一个个对比---------

class Solution {
public:
    bool canPlaceFlowers(vector<int>& flowerbed, int n) {
        bool isBeforeNoFlower = true;
        int planted = 0;
        for(int i=0;i< flowerbed.size(); ++i)
        {
            if(flowerbed[i] == 1){
                isBeforeNoFlower = false;
            }else{
                if(isBeforeNoFlower){ // before condition meet
                    if(i == flowerbed.size()-1 || flowerbed[i+1]==0) // check next step condition
                    {
                        ++planted;
                        isBeforeNoFlower = false;
                    }
                }else{
                    isBeforeNoFlower = true;
                }
            }            
            if(planted>=n)//canot check inside if statement, thus we need also check here
                return true;
        }
        return false; 
    }
};

Mistakes：

1：  忘了要考虑后面的位置

2：   没有考虑 n==0 的情况， 因此， 最后也需要考虑