[LeetCode 335] Self Crossing

You are given an array x of n positive numbers. You start at point (0, 0) and moves x[0] metres to the north, then x[1] metres to the west, x[2] metres to the south, x[3] metres to the east and so on. In other words, after each move your direction changes counter-clockwise.

Write a one-pass algorithm with O(1) extra space to determine, if your path crosses itself, or not.

Example 1:

Given x = 
[2, 1, 1, 2]
,
┌───┐
│   │
└───┼──>
    │

Return true (self crossing)

Example 2:

Given x = 
[1, 2, 3, 4]
,
┌──────┐
│      │
│
│
└────────────>

Return false (not self crossing)

Example 3:

Given x = 
[1, 1, 1, 1]
,
┌───┐
│   │
└───┼>

Return true (self crossing)

Diffculty
Hard

Similar Problems

Analysis