335. Self Crossing

Problem

You are given an array of integers distance.

You start at point (0,0) on an X-Y plane and you move distance[0] meters to the north, then distance[1] meters to the west, distance[2] meters to the south, distance[3] meters to the east, and so on. In other words, after each move, your direction changes counter-clockwise.

Return true if your path crosses itself, and false if it does not.

  Example 1:

Input: distance = [2,1,1,2]
Output: true

Example 2:

Input: distance = [1,2,3,4]
Output: false

Example 3:

Input: distance = [1,1,1,1]
Output: true

  Constraints:

• 1 <=&nbsp;distance.length <= 10^5

• 1 <=&nbsp;distance[i] <= 10^5

Solution

/**
 * @param {number[]} distance
 * @return {boolean}
 */
var isSelfCrossing = function(distance) {
    for ( var i = 3; i < distance.length; i++ ){
    // i. [2, 1, 1, 2] 
    if (distance[i - 3] && distance[i] >= distance[i - 2] && distance[i - 1] <= distance[i - 3 ]) 
      return  true ;
    // ii. [1, 1, 2, 1, 1] 
    if (distance[i - 4] && distance[i - 3] === distance[i - 1] && distance[ i - 4] + distance[i] >= distance[i - 2 ]) 
      return true ;
    // iii. [1, 1, 2, 2, 1, 1] 
    if (distance[i - 5] && distance[i - 4] <= distance[i -2] && distance[i] + distance[i - 4] >= distance[i -2 ] 
      && distance[i - 3] >= distance[i - 1] && distance[i - 5] + distance[i - 1] >= distance[i - 3 ]) 
      return  true ;
    }
    return  false ;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).