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https://leetcode.com/problems/robot-bounded-in-circle
On an infinite plane, a robot initially stands at (0, 0)
and faces north. The robot can receive one of three instructions:
"G"
: go straight 1 unit;
"L"
: turn 90 degrees to the left;
"R"
: turn 90 degrees to the right.
The robot performs the instructions
given in order, and repeats them forever.
Return true
if and only if there exists a circle in the plane such that the robot never leaves the circle.
Example 1:
Example 2:
Example 3:
Constraints:
1 <= instructions.length <= 100
instructions[i]
is 'G'
, 'L'
or, 'R'
.
Mostly a brain teaser: return true if after executing instuctions, 1) back to stating point; 2) not facing up. See proof below.
Solution explain: https://leetcode.com/problems/robot-bounded-in-circle/discuss/290856/JavaC%2B%2BPython-Let-Chopper-Help-Explain
Proof: