Permutation in a String (hard)

[Lee_Min_Han]

Link: https://www.educative.io/courses/grokking-the-coding-interview/N8vB7OVYo2D#permutation-in-a-string-hard

Hi there! I don’t quite understand why line 22 is wrong? Am I not ensuring that window size will always <= length of pattern?

Thanks in advance!