657-easy-Judge_Route_Circle.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}
 */
var judgeCircle = function(moves) {
  if (!moves.length) {
    return true;
  } else if (moves.length % 2) {
    return false;
  }
  let x = y = 0;
  for(let i = 0, len = moves.length; i < len; i++) {
    switch (moves[i]) {
      case 'R':
        x += 1;
        break;
      case 'L':
        x -= 1;
        break;
      case 'U':
        y += 1;
        break;
      case 'D':
        y -= 1;
        break;
      default:
        // statements_def
        break;
    }
  }

  return (x === 0 && y === 0) ? true : false;
};