Number Theory on Data Structure and Algorithms related Questions and Answers

Question :   What will be the lexicographical order of combinations of 2 elements each formed from the array arr={1,2,3}? 1. {{2,1},{3,2},{3,1}} 2. {{1,2},{2,3},{1,3}} 3. {{1,2},{1,3},{2,3}} 4. {{2,1},{3,1},{3,2}} Answer :   3 - {{1,2},{1,3},{2,3}}