give two sorted array, find the k-th smallest element of union of A and B
Giveyoutwosortedarray,findthek-thsmallestelementsofunionofAandB,youcanassumethattherearenoduplicateelements.thesizeofAism,andsizeofBisn,boththemareinacsendingorder.Atfirst,wecanusebrute-force, malloca