Self Crossing Problem


Description

LeetCode Problem 335.

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:

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

Example 2:

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

Example 3:

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

Constraints:

  • 1 <=distance.length <= 10^5
  • 1 <=distance[i] <= 10^5


Sample C++ Code

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
class Solution {
public:
    bool isSelfCrossing(vector<int>& x) {
        x.insert(x.begin(), 4, 0);

        int len = x.size();
        int i = 4;

        // outer spiral
        for (; i < len && x[i] > x[i - 2]; i++);

        if (i == len) return false;

        // check border
        if (x[i] >= x[i - 2] - x[i - 4]) {
            x[i - 1] -= x[i - 3];
        }

        // inner spiral
        for (i++; i < len && x[i] < x[i - 2]; i++);

        return i != len;
    }
};




Related Posts

Beautiful Arrangement II Problem

LeetCode 667. Given two integers n and k, construct a...

Range Addition II Problem

LeetCode 598. You are given an m x n matrix...

Perfect Number Problem

LeetCode 507. A perfect number is a positive integer that...

Optimal Division Problem

LeetCode 553. You are given an integer array nums. The...

Minimum Time Difference Problem

LeetCode 539. Given a list of 24-hour clock time points...

Minimum Moves To Equal Array Elements Problem

LeetCode 453. Given an integer array nums of size n,...