643. Maximum Average Subarray I(python+cpp)
阿新 • • 發佈:2018-11-03
題目:
Given an array consisting of
n
integers, find the contiguous subarray of given lengthk
that has the maximum average value. And you need to output the maximum average value.
Example 1:Input: [1,12,-5,-6,50,3], k = 4 Output: 12.75 Explanation: Maximum average is (12-5-6+50)/4 = 51/4 = 12.75
Note:
1 <= k <= n <= 30,000
.
Elements of the given array will be in the range[-10,000,10,000]
.
解釋:
找到陣列nums
中均值長度為k
的均值最大的subarray的均值,需要注意的是,subsrray是連續的陣列。
不用每次都計算和,首先求出最開始k
個數字的和,然後每次只要加上後一個數,再加上後一個數就是新的和了。
python程式碼:
class Solution(object):
def findMaxAverage(self, nums, k):
"""
:type nums: List[int]
:type k: int
:rtype: float
"""
last_sum=sum(nums[0:k])
max_sum=last_sum
for i in xrange(len(nums)-k):
last_sum=last_sum+nums[i+k]-nums[i]
max_sum=max(max_sum,last_sum)
return max_sum/float(k)
c++程式碼:
class Solution {
public:
double findMaxAverage(vector<int>& nums, int k) {
double last_sum=accumulate(nums.begin(),nums.begin()+k,0);
double max_sum=last_sum;
for (int i=0;i<nums.size()-k;i++)
{
last_sum+=nums[i+k]-nums[i];
max_sum=max(max_sum,last_sum);
}
return max_sum/k;
}
};
總結:
c++剛開始用int
結果最後小數點後幾位精度不對,改成double以後就好了。