Solution 1 by cases

• t-complexity: $O(n)$

• s-complexity: %O(1)%

three cases that will not self crossing:

• always out: dist[i] > dist[i-2]

• always in: dist[i] < dist[i-2]

• first out then in:

see graph at: https://leetcode-cn.com/problems/self-crossing/solution/tong-ge-lai-shua-ti-la-san-chong-bu-xian-w80r/