[leetcode]605. Can Place Flowers能放花吗

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.

 

题意：

给定一个花圃（1代表已种有花，0表示空）， 规定花不能相邻。 问新来的n束花能否被种到该花圃。

 

Solution1： Greedy

扫给定数组，只要满足条件就插个1（种朵花）， 直到n==0(新来花都种下了) 或者数组扫完。

明显的，扫到一个坑为0， 且其左边为0，右边为0， 该坑就可以种花

同时注意左右边界的特殊处理， （1）如果该坑为front， 且其右边为0， 该坑可以种花

                                          （2）如果该坑为tail， 且其左边为0， 该坑可以种花

 

 

code

class Solution {
    public boolean canPlaceFlowers(int[] flowerbed, int n) {  
        int i = 0;
        while( i < flowerbed.length && n > 0 ){
            if (flowerbed[i]==0 && (i==0 || flowerbed[i-1]==0) &&  (i==flowerbed.length-1 || flowerbed[i+1]==0)){
                flowerbed [i] = 1;
                n--;
            }
            i++;
        }
        return n == 0;
    }
}