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: 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.

/*
比较当前位置左右两边的数是否为0且当前位置是0，是count++；
但最重要的是处理好首尾两端，eg：[0,0,1,0,0];以及当len<=3的情况
*/

class Solution {
    public boolean canPlaceFlowers(int[] flowerbed, int n) {
        int count=0,len=flowerbed.length;
     //处理len<=3 and 首尾两端 的情况
        if (len==1 && flowerbed[0]==0) {
            return 1>=n;
        }
        if (len==1 && flowerbed[0]==1) {
            return 0>=n;
        }

        if (flowerbed[0]==0 && flowerbed[1]==0) 
        {   
            count++;
            flowerbed[0]=1;
        }
        if (flowerbed[len-1]==0 && flowerbed[len-2]==0) 
        {   
            count++;
            flowerbed[len-1]=1;
        }
    //len>=3 的情况
        for (int i =1; i < len-1 && len>=3; i++) {
            if(flowerbed[i-1]==0 && flowerbed[i+1]==0 && flowerbed[i]==0)
            {   
                flowerbed[i]=1; 
                count++;
            }
        }

    return count>=n;
    }
}