Toolbox

Some general suggestions for problem solving:

  • Exploit Symmetry
  • Work backward
  • While counting, look at things from different angles and always try to exchange order of summation
  • Try smaller problems, lower dimensions, extreme cases

General principles:

  • Pigeonhole principle (Dirichlet)
  • Parity checks (odd vs. even)
  • Apply arithmetic modulo N, remember your divisibility criteria
  • Induction, strong induction
  • Use of geometric transformations

Links:

Terry Tao on problem solving