Given an array $A$, find all quadruples $(i,j,k,ell)$ such that $i＜j＜k＜ell$ and $A[i]=A[k]$ and...
Channel: Roel Van de Paar
Date: 2021-02-09

Given an array $A$, find all quadruples $(i,j,k,ell)$ such that $i＜j＜k＜ell$ and $A[i]=A[k]$ and $A[j]=A[ell]$?

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