643.子数组最大平均数

1.TLE

class Solution {
public:
    // 返回集合所有元素的和
    double sum(queue<double> q)
    {
        double res = 0;
        while(q.size())
        {
          res += q.front();
          q.pop();
        }

        return res;
    }

    double findMaxAverage(vector<int>& nums, int k) {
        // 滑动窗口
        int n = nums.size();

        if(n == 1) return nums[0] / k;

        queue<double> q;
        double res = 0;

        for(int i = 0; i < n; i++)
        {
            // 超出范围
            if(i >= k) q.pop();
            
            q.push(nums[i]);

            if(q.size() == k) res = max(res, sum(q));
        }

        return res / k;
    }
};

2.前缀和

class Solution {
public:
    static const int N = 1e5 + 10;
    int s[N];

    double findMaxAverage(vector<int>& nums, int k) {
      // 特殊情况
      int n = nums.size();
      if(n == 1) return (double) nums[0] / k;

      // 前缀和
      s[0] = 0;
      for(int i = 1; i <= n; i++)
      {
        s[i] = s[i - 1] + nums[i - 1];
      }
      
      int sum = -2e9;
      for(int i = k, j = 0; i <= n; i++, j++)
      {
        sum = max(sum, s[i] - s[j]);
      }

      return (double) sum / k;
    }
};