2019 Dec Bronze Problem 3 Livestock Lineup

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Official Problem Statement[edit]

Livestock Lineup

Problem Statement[edit]

The USACO 965 problem, Livestock Lineup, is a classic problem of sorting. Given a list of N (1 ≤ N ≤ 10,000) cows, each with a unique ID number from 1 to N, you must arrange them in a line such that the absolute difference between the ID numbers of any two adjacent cows is as small as possible.

Solution[edit]

The solution to this problem is to sort the cows in ascending order according to their ID numbers. This can be done using a C++ implementation of the quicksort algorithm.

// C++ implementation of quicksort algorithm

void quicksort(int arr[], int left, int right) {

   int i = left, j = right; 
   int tmp; 
   int pivot = arr[(left + right) / 2]; 
 
   /* partition */
   while (i <= j) { 
       while (arr[i] < pivot) 
           i++; 
       while (arr[j] > pivot) 
           j--; 
       if (i <= j) { 
           tmp = arr[i]; 
           arr[i] = arr[j]; 
           arr[j] = tmp; 
           i++; 
           j--; 
       } 
   }; 
 
   /* recursion */
   if (left < j) 
       quicksort(arr, left, j); 
   if (i < right) 
       quicksort(arr, i, right); 

}