Who decides the presidential election of no electoral college is not clear?

The grammar got a little mangled there, but:

If no candidate winds up with an absolute majority of the electoral college, the election for President is decided by the US House of Representatives. The only choices available to the House of Representatives are those candidates placing in the top three of the electoral college vote. In the House vote, each state receives one vote (regardless of the number of representatives it has) and must cast its vote for one of the three choices (or abstain from voting). In order to win, a candidate must receive an absolute majority (that is, at least 26 votes out of the possible total of 50, one for each state). If no candidate receives an absolute majority, voting continues until one of the candidates does.

The election for Vice-President is run separately by the Senate, though in this case only the top TWO candidates in the electoral college vote are options. Each Senator receives an individual vote (the two Senators from a state are not required to vote for the same candidate). An absolute majority (usually 51 votes of a possible 100, 2 for each state) is required to win. Again, if no candidate gets at least 51 votes, then the Senate continues voting until a winner is chosen.

In both cases, a 2/3 majority of the state delegations (House) or Senators (Senate) must be present for the vote to take place at all. Regardless of the number of votes cast, an absolute majority of the possible votes is required to win.

In both cases, this disproportionately favors less populous states; Alaska (population well under a million) gets the same number of votes as California (population almost 39 million).

It IS possible that the vote could stall in the House until after the date when the new president should be inaugurated; in that case, the newly elected Vice-President would become Acting President until such time as the House vote was resolved. If neither the House nor the Senate had made a final determination by then, the Speaker of the House would become Acting President until either the Senate elected a Vice-President (who would then become Acting President) or the House elected a President (who would then become President).

Incidentally, if you're a fan of the HBO series "Veep", the scenario in the season 5 finale cannot happen in real life. The major inaccuracies are that in the case of a tie in the House, it does not automatically result in the Senate's choice for Vice President becoming President (Acting President possibly, but not actually President), and if there is a tie in the Senate, there is at the very least a legal gray area as to whether or not the President of the Senate (who is not actually a Senator) is allowed to cast the tie-breaking vote.