Path Crossing

Description

Given a string path, where path[i] = 'N', 'S', 'E' or 'W', each representing moving one unit north, south, east, or west, respectively. You start at the origin (0, 0) on a 2D plane and walk on the path specified by path.

Return True if the path crosses itself at any point, that is, if at any time you are on a location you've previously visited. Return False otherwise.

 

Example 1:

Input: path = "NES"
Output: false 
Explanation: Notice that the path doesn't cross any point more than once.

Example 2:

Input: path = "NESWW"
Output: true
Explanation: Notice that the path visits the origin twice.

 

Constraints:

• 1 <= path.length <= 10^4
• path will only consist of characters in {'N', 'S', 'E', 'W}

Solution(javascript)

/**
 * @param {string} path
 * @return {boolean}
 */
const isPathCrossing = function (path) {
  const set = new Set()
  let x = 0
  let y = 0
  for (const c of path) {
    if (c === 'N') {
      y += 1
    } else if (c === 'S') {
      y -= 1
    } else if (c === 'W') {
      x -= 1
    } else {
      x += 1
    }
    if (x === 0 && y === 0) {
      return true
    }
    const point = `${x}-${y}`
    if (set.has(point)) {
      return true
    }
    set.add(point)
  }
  return false
}