EN Combinatorial problems reflect some of the core situations of both theoretical and engineering computer science. To find broad classes of problems which can be effectively solved is of pivotal importance and this in turn leads to some popular dichotomies. We survey the recent development particularly from the point of view of the sparse vs dense dichotomy. CZ Kombinatorické problémy modelují mnohé důležité situace z teoretické i aplikované informatiky. Nalezení širokých tříd problémů, které…