[LeetCode] 605. Can Place Flowers

Problem

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.

Solution

class Solution {
    public boolean canPlaceFlowers(int[] bed, int n) {
        if (bed == null || bed.length == 0) return n == 0;
        if (n > (bed.length+1)/2) return false;
        if (bed.length == 1) return !(bed[0] == 1 && n >= 1);
        int i = 0, k = n;
        while (i < bed.length && k > 0) {
            if (bed[i] == 1) i+=2;
            else {
                if (i > 0 && i < bed.length-1) {
                    if (bed[i-1] == 0 && bed[i+1] == 0) {
                        bed[i] = 1;
                        k--;
                    }
                } else if (i == 0) {
                    if (bed[i+1] != 1) {
                        bed[i] = 1;
                        k--;
                    }
                } else {
                    if (bed[i-1] != 1) {
                        bed[i] = 1;
                        k--;
                    }
                }
                i++;
            }
        }
        return k <= 0;
    }
}