Given an array of integers arr and two integers k and threshold, return the number of sub-arrays of size k and average greater than or equal to threshold.
Example 1:
Input: arr = [2,2,2,2,5,5,5,8], k = 3, threshold = 4
Output: 3
Explanation: Sub-arrays [2,5,5],[5,5,5] and [5,5,8] have averages 4, 5 and 6 respectively. All other sub-arrays of size 3 have averages less than 4 (the threshold).
Example 2:
Input: arr = [11,13,17,23,29,31,7,5,2,3], k = 3, threshold = 5
Output: 6
Explanation: The first 6 sub-arrays of size 3 have averages greater than 5. Note that averages are not integers.
Constraints:
1 <= arr.length <= 105
1 <= arr[i] <= 104
1 <= k <= arr.length
0 <= threshold <= 104
大小为 K 且平均值大于等于阈值的子数组数目。
给你一个整数数组 arr 和两个整数 k 和 threshold 。请你返回长度为 k 且平均值大于等于 threshold 的子数组数目。
思路
这道题是一道窗口尺寸固定的滑动窗口题。注意尽量不要在中间过程求平均值因为会涉及到精度问题。在过程中我们可以只求数字的 sum,不求平均值,到最后再计算平均值。
复杂度
时间O(n)
空间O(1)
代码
Java实现
class Solution {
public int numOfSubarrays(int[] arr, int k, int threshold) {
int n = arr.length;
int sum = 0;
for (int i = 0; i < k; i++) {
sum += arr[i];
}
int res = 0;
if (sum >= threshold * k) {
res++;
}
for (int i = k; i < n; i++) {
sum += arr[i];
sum -= arr[i - k];
if (sum >= threshold * k) {
res++;
}
}
return res;
}
}
标签:arr,Sub,arrays,Average,than,int,threshold,sum
From: https://www.cnblogs.com/cnoodle/p/18537603