Question

335. Self Crossing

中文文档

Description

You are given an array of integers distance .

You start at the 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 or _ false _ if it does not_.

Example 1:

Input: distance = [2,1,1,2]
Output: true
Explanation: The path crosses itself at the point (0, 1).

Example 2:

Input: distance = [1,2,3,4]
Output: false
Explanation: The path does not cross itself at any point.

Example 3:

Input: distance = [1,1,1,2,1]
Output: true
Explanation: The path crosses itself at the point (0, 0).

Constraints:

• 1 <= distance.length <= 105
• 1 <= distance[i] <= 105

Solutions

Solution 1

class Solution:
  def isSelfCrossing(self, distance: List[int]) -> bool:
    d = distance
    for i in range(3, len(d)):
      if d[i] >= d[i - 2] and d[i - 1] <= d[i - 3]:
        return True
      if i >= 4 and d[i - 1] == d[i - 3] and d[i] + d[i - 4] >= d[i - 2]:
        return True
      if (
        i >= 5
        and d[i - 2] >= d[i - 4]
        and d[i - 1] <= d[i - 3]
        and d[i] >= d[i - 2] - d[i - 4]
        and d[i - 1] + d[i - 5] >= d[i - 3]
      ):
        return True
    return False

class Solution {
  public boolean isSelfCrossing(int[] distance) {
    int[] d = distance;
    for (int i = 3; i < d.length; ++i) {
      if (d[i] >= d[i - 2] && d[i - 1] <= d[i - 3]) {
        return true;
      }
      if (i >= 4 && d[i - 1] == d[i - 3] && d[i] + d[i - 4] >= d[i - 2]) {
        return true;
      }
      if (i >= 5 && d[i - 2] >= d[i - 4] && d[i - 1] <= d[i - 3]
        && d[i] >= d[i - 2] - d[i - 4] && d[i - 1] + d[i - 5] >= d[i - 3]) {
        return true;
      }
    }
    return false;
  }
}

class Solution {
public:
  bool isSelfCrossing(vector<int>& distance) {
    vector<int> d = distance;
    for (int i = 3; i < d.size(); ++i) {
      if (d[i] >= d[i - 2] && d[i - 1] <= d[i - 3]) return true;
      if (i >= 4 && d[i - 1] == d[i - 3] && d[i] + d[i - 4] >= d[i - 2]) return true;
      if (i >= 5 && d[i - 2] >= d[i - 4] && d[i - 1] <= d[i - 3] && d[i] >= d[i - 2] - d[i - 4] && d[i - 1] + d[i - 5] >= d[i - 3]) return true;
    }
    return false;
  }
};

func isSelfCrossing(distance []int) bool {
  d := distance
  for i := 3; i < len(d); i++ {
    if d[i] >= d[i-2] && d[i-1] <= d[i-3] {
      return true
    }
    if i >= 4 && d[i-1] == d[i-3] && d[i]+d[i-4] >= d[i-2] {
      return true
    }
    if i >= 5 && d[i-2] >= d[i-4] && d[i-1] <= d[i-3] && d[i] >= d[i-2]-d[i-4] && d[i-1]+d[i-5] >= d[i-3] {
      return true
    }
  }
  return false
}

public class Solution {
  public bool IsSelfCrossing(int[] x) {
    for (var i = 3; i < x.Length; ++i)
    {
      if (x[i] >= x[i - 2] && x[i - 1] <= x[i - 3]) return true;
      if (i > 3 && x[i] + x[i - 4] >= x[i - 2])
      {
        if (x[i - 1] == x[i - 3]) return true;
        if (i > 4 && x[i - 2] >= x[i - 4] && x[i - 1] <= x[i - 3] && x[i - 1] + x[i - 5] >= x[i - 3]) return true;
      }
    }
    return false;
  }
}