Determine the Widest Valley
Python 2, 120 115 89 87 86 152 149 bytes



lambda a:max(r-l+1for l,v in e(a)for r,w in e(a)if max(a[l+1:r]+[0])&lt;v==w*any(s(a[l:i])[::-1]+s(a[i:r])==a[l:r]for i,_ in e(a)));e=enumerate;s=sorted


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