Primary school students Blue Bridge Cup Python breakthrough | monotone queue - sliding window maximum

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【Description】

Given an array of length n and a sliding window of size m (0<m≤n), please find the maximum value in all sliding windows.

For example, the array {2,6,4,9,8,5,5,2}, the size of the sliding window is 3, then there are 6 sliding windows, and their maximum values ​​are 6,9,9,9, 8,5.

【Code Explanation】

a = [0,2,6,4,9,8,5,5,2]
m = 3

for i in range(m, len(a)):
    mx = a[i]
    for j in range(i-m+1, i+1):
        mx = max(mx, a[j])
    print(mx)
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#单调队列
a = [0,2,6,4,9,8,5,5,2]
q = [0,1,2,3,4,5,6,7,8]
m = 3

h = 0
t = -1
for i in range(1, len(a)):
    #q[h]不在窗口[i-m+1]内，队头出队
    if h<=t and q[h]<i-m+1:
        h += 1
    #当前值>=队尾值，队尾出队
    while h<=t and a[i]>=a[q[t]]:
        t -= 1
    #下标入队，便于队头出队
    t+=1
    q[t] = i
    #使用队头最大值
    if i > m - 1: #满3个时才输出
        print(a[q[h]])
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【operation result】

6
9
9
9
8
5