Leetcode

Leetcode - 605 - Can Place Flowers

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:

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.

题解： 

　　注意前面一段和后面一段。

class Solution {
public:
    bool canPlaceFlowers(vector<int>& flowerbed, int n) {
        int cnt, ans = 0, st = -1, ed = flowerbed.size()-1; 
        for(int i=0; i<=ed; ++i){
            if(flowerbed[i] == 1){
                cnt = i - 1 - st; 
                if(cnt > 0){
                    ans += cnt/2; 
                }
                st = i + 1; 
            }
        }
        if(flowerbed[ed] != 1){
            cnt = ed + 1 - st; 
            if(cnt > 0){
                ans += cnt/2; 
            }
        }
        return (ans >= n); 
    }
};