monotonous queue implementation

monotonous queue

  8 const int LEN = 3;
  9 struct node{
 10     int val;
 11     int seq;
 12 }monoto_Q[LEN];
 13
 14 void findAscend_MonotonousQueue(int arr[], int len, int qSize){
 15     if (arr == NULL || len <= LEN)
 16         return;
 17     int index = 0, tail = 0, head = 1;
 18
 19     //initialize the monotonous queue
 20     for (index = 0; index < qSize; ++index){
 21         while (head <= tail && arr[index] > monoto_Q[tail].val){
 22                 --tail;
 23         }
 24         monoto_Q[++tail].val = arr[index];
 25         monoto_Q[tail].seq = index;
 26     }
 27
 28     //handle the data array
 29     for (index = qSize - 1; index < len; ++index){
 30         while (head <= tail && arr[index] > monoto_Q[tail - 1].val){
 31                 --tail;
 32         }
 33         monoto_Q[++tail].val = arr[index];
 34         monoto_Q[tail].seq = index;
 35         while (index - monoto_Q[head].seq > qSize - 1)
 36                 ++head;
 37         cout << monoto_Q[head].val << " ";
 38     }
 39     cout << endl;
 40 }