（leetcode题解）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.

这道题采用贪心算法，满足连续三个零就是一个符合点，一次遍历即可，首尾的边界问题（只需要两个连续零）不能忽略。 

C++实现如下：

bool canPlaceFlowers(vector<int>& flowerbed, int n) {
        int length=flowerbed.size();
        int count=0;
        for(int i=0;i<length;)
        {
            while(flowerbed[i]==0)
            {
                i++;
                if((i==length-1||i==1)&&flowerbed[i]==0)    
                    count++;
                else if(i<length-1&&flowerbed[i]==0&&flowerbed[++i]==0)
                    count++;
            }
            i++;
            if(n<=count)
                return true; 
        }
        return false;
    }