Friday, March 6, 2020

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.

A:

             -------------就是一个个对比---------
class Solution {
public:
    bool canPlaceFlowers(vector<int>& flowerbed, int n) {
        bool isBeforeNoFlower = true;
        int planted = 0;
        for(int i=0;i< flowerbed.size(); ++i)
        {
            if(flowerbed[i] == 1){
                isBeforeNoFlower = false;
            }else{
                if(isBeforeNoFlower){ // before condition meet
                    if(i == flowerbed.size()-1 || flowerbed[i+1]==0) // check next step condition
                    {
                        ++planted;
                        isBeforeNoFlower = false;
                    }
                }else{
                    isBeforeNoFlower = true;
                }
            }            
            if(planted>=n)//canot check inside if statement, thus we need also check here
                return true;
        }
        return false; 
    }
};

Mistakes:
1:  忘了要考虑后面的位置
2:   没有考虑 n==0 的情况, 因此, 最后也需要考虑


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