leetcode解题: Can Place Flowers (605)

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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:

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Input: flowerbed = [1,0,0,0,1], n = 1
Output: True

Example 2:

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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.

解法1：

Java

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public class Solution {
    public boolean canPlaceFlowers(int[] flowerbed, int n) {
        
        if (flowerbed == null || flowerbed.length == 0) {
            return false;
        }        
        
        // traverse from left to right
        int i = 0;
        int size = flowerbed.length;
        
        while (n > 0) {
            if (i < size && flowerbed[i] == 1) {
                i += 2;
            } else if (i >= size) {
                break;
            } else {
                // check left & right 
                if ((i == 0 || flowerbed[i - 1] == 0) && (i == size - 1 || flowerbed[i + 1] == 0)) {
                    flowerbed[i] = 1;
                    n--;
                    i += 2;
                } else {
                    i += 1;
                }
            }
        }
        
        return n == 0;
    }
}