Given a array of integers , find 3 indexes i, j, k such that, i<j<k and a[i] < a[j]< a[k]. Could you find possible O(n) algorithm.

findAscend.cpp

/*
* @func: find the ascends element from array
* @params: arr{array}, the given array,
*          len{int}, the length of array
*          pos{int}, the first position that finding the ascending elements 
*/
 43 void findAscend_(int arr[], int len, int pos){
 44     int index_array[ARRLEN] = {0};
 45     int current_max = 0;
 46     int current_max_index = 0;
 47     if (arr == NULL || pos >= len)
 48             return ;
 49
 50     //initialize the index array. traverse the array from back to front
 51     for (int index = len - 1; index >= 0; --index){
 52         if (arr[index] > current_max){
 53             current_max_index = index;
 54             current_max = arr[index];
 55         }
 56         index_array[index] = current_max_index;
 57     }
 58
 59     int current = arr[pos];
 60     for (int index = pos; index < len - 1; ++index){
 61         if (arr[index] > current && index_array[index] > index)
 62         {
 63             cout << "the ascends are: " << current << " "
 64                     << arr[index] << " "
 65                     << arr[index_array[index]] << endl;
 66             return;
 67         }
 68     }
 69 }