judgeCircle.js

/*
Initially, there is a Robot at position (0, 0). Given a sequence of its moves, judge if this robot makes a circle, which means it moves back to the original place.

The move sequence is represented by a string. And each move is represent by a character. The valid robot moves are R (Right), L (Left), U (Up) and D (down). The output should be true or false representing whether the robot makes a circle.

Example 1:
Input: "UD"
Output: true

Example 2:
Input: "LL"
Output: false

*/
/**
 * @param {string} moves
 * @return {boolean}
**/

const judgeCircle = function(moves) {
    let vertical = 0, horizontal = 0;
    for (let i = 0; i < moves.length; i++) {
        if (moves[i] === "U") {
            vertical++;
        } else if (moves[i] === "D") {
            vertical--;
        } else if (moves[i] === "L") {
            horizontal--;
        } else if (moves[i] === "R") {
            horizontal++;
        }
    }
    return (vertical === 0 && horizontal === 0);
};