Learning notes: Monotone queue

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The monotone queue solves the problem of the maximum value of an interval segment in a sequence, and we can use the monotone queue to solve it.
For example, poj2823 Sliding Window is a good example: given a sequence, the maximum and minimum values in a range of fixed length k in a sequence are required.
The "principle" monotone queue maintains the maximum interval:
1and maintenance of the maximum value:
For example, we want to maintain a monotone queue with a maximum interval of k, because the newly inserted node his "vitality" is certainly longer than the element that was already in the queue, will be inserted element continuously with the team tail element, if he is larger than the tail element, then r--the tail element to delete,(because the currently inserted value of this element (set to POS) is larger, and "live" time is long, there is POS, the tail element of the "life" of the year will never be the maximum value, so directly ignoring the lower end of the queue than the POS) . Until the empty position or find a larger than the point of the end of the queue.
2, the maintenance of K-zone:
For example, the starting point of the K interval is I, that is, the interval is [i,i+k-1], then if the team head element front subscript j<i, then the front will not meet in the current K range, then his value is not the current K range of the maximum value, so f++ Will head out of the team. This operation will never encounter a team empty situation, should be a 1th step has been inserted in the interval for [i,i+k-1] element Pos, he subscript J must conform to J>=i

"Template Code"

1 struct nodes   2  3     int4 5 6 7  int

Descending queue:

1 voidInsertintMintIdintL//L is the leftmost subscript of the interval, m the value to insert, the index of the value of the ID2 { 3      while(r1>=f1&&m>qu1[r1].val)4r1--; 5Qu1[++r1].val=m;6qu1[r1].beg=ID;7      while(qu1[f1].beg<L)8f1++; 9 } Ten  One //f>r qu Empty AInit:f=r=0;  -  -Insert (A[I],I,L);

Increment to make the corresponding changes can be

Summarize:

The monotonous queue uses the changeable, in the concrete question, should use flexibly ~

Learning notes: Monotone queue