Cinte's Leetcode Record
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198. House Robber

Posted on Edited on In Disqus:
Symbols count in article: 686 Reading time ≈ 1 mins.

198. House Robber

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class Solution {
public:
    int rob(vector<int>& nums) {
        if(nums.size() == 1) return nums[0];
        vector<int> dp(nums.size());
        dp[0] = nums[0];
        dp[1] = max(nums[0], nums[1]);
        for(int i = 2; i < nums.size(); ++i)
        {
            dp[i] = max(nums[i] + dp[i - 2], dp[i - 1]);
        }
        return dp.back();
    }
};

T(n) : O(n)
S(n) : O(n)

注意到每次只用到dp[i - 2]和dp[i - 1],用2变量优化
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class Solution {
public:
    int rob(vector<int>& nums) {
        if(nums.size() == 1) return nums[0];
        int dp[2];
        dp[0] = nums[0];
        dp[1] = max(nums[0], nums[1]);
        for(int i = 2; i < nums.size(); ++i)
        {
            dp[0] = max(nums[i] + dp[0], dp[1]);
            swap(dp[0], dp[1]);
        }
        return dp[1];
    }
};

T(n) : O(n)
S(n) : O(1)

dicussion中的动态规划推导步骤