力扣每日一题

605. 种花问题 - 力扣（LeetCode）

动态规划

class Solution {
public:
    bool canPlaceFlowers(vector& flowerbed, int n) 
    {
        int m = flowerbed.size();
        if(1 == m)return !flowerbed[0] >= n;
        else if(2 == m)return ((!flowerbed[0] && !flowerbed[1]) >= n);
        int dp[m][2];//第i个位置种|不种最大的收获数
        memset(dp, 0, sizeof dp);
        if(!flowerbed[0] && !flowerbed[1])
        {
            dp[0][1] = 1;
            dp[1][0] = 1;
            dp[1][1] = 1 - flowerbed[2];
        }
        for(int i = 2; i < m - 1; i++)
        {
            if(!flowerbed[i] && !flowerbed[i + 1] && !flowerbed[i - 1])
            {
                dp[i][1] = max(dp[i - 1][1], dp[i - 1][0] + 1);
                dp[i][0] = dp[i - 1][1];
            }
            else
            {
                dp[i][1] = max(dp[i - 1][1], dp[i - 1][0]);
                dp[i][0] = max(dp[i - 1][1], dp[i - 2][1]);
            }
        }
        if(!flowerbed[m - 1] && !flowerbed[m - 2])
        {
            dp[m - 1][1] = max(dp[m - 2][0] + 1,dp[m - 2][0]);
            dp[m - 1][0] = max(dp[m - 1][1], dp[m - 2][1]);
        }
        else
        dp[m - 1][0] = max(dp[m - 2][1],dp[m - 2][0]);
        return max(dp[m - 1][0], dp[m - 1][1]) >= n;
    }
};

贪心

class Solution {
public:
    bool canPlaceFlowers(vector &flowerbed, int n) 
    {
        int m = flowerbed.size();
        flowerbed.insert(flowerbed.begin(),0);
        flowerbed.emplace_back(0);
        for(int i = 1; i <= m; i++)
        {
            if(!flowerbed[i] && !flowerbed[i - 1] && !flowerbed[i + 1])
            {
                flowerbed[i] = 1;
                n--;
            }
        }
        return n <= 0;
    }
};