Track horizontal and vertical displacement while scanning the move string, then test whether both coordinates are zero.
Complexity
O(n) time and O(1) extra space.
09 Sept 2026•Easy•Go / Python / TypeScript
Robot Return to Origin
Check whether a sequence of unit moves returns a robot to its starting point.
Solution files
Go•robot-return-to-origin/solution.go
package main
func judgeCircle(moves string) bool {
horizontal, vertical := 0, 0
for _, move := range moves {
switch move {
case 'L':
horizontal--
case 'R':
horizontal++
case 'U':
vertical++
case 'D':
vertical--
}
}
return horizontal == 0 && vertical == 0
}
Python•robot-return-to-origin/solution.py
class Solution:
def judgeCircle(self, moves: str) -> bool:
horizontal = vertical = 0
for move in moves:
if move == "L": horizontal -= 1
elif move == "R": horizontal += 1
elif move == "U": vertical += 1
else: vertical -= 1
return horizontal == 0 and vertical == 0
TypeScript•robot-return-to-origin/solution.ts
function judgeCircle(moves: string): boolean {
let horizontal = 0;
let vertical = 0;
for (const move of moves) {
if (move === "L") horizontal -= 1;
else if (move === "R") horizontal += 1;
else if (move === "U") vertical += 1;
else vertical -= 1;
}
return horizontal === 0 && vertical === 0;
}