组合数学 (Fall 2023)/Problem Set 3
Problem 1
Solve the following two existence problems:
- You are given [math]\displaystyle{ n }[/math] integers [math]\displaystyle{ a_1,a_2,\dots,a_n }[/math], such that for each [math]\displaystyle{ 1\leq i\leq n }[/math] it holds that [math]\displaystyle{ i-n\leq a_i\leq i-1 }[/math]. Show that there exists a nonempty subset of these integers, whose sum is equal to [math]\displaystyle{ 0 }[/math].