LeetCode //C - 335. Self Crossing

335. Self Crossing

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:

Example 2:

Example 3:

Constraints:

• 1 < = d i s t a n c e . l e n g t h < = 1 0 5 1 <= distance.length <= 10^5 1<=distance.length<=105
• 1 < = d i s t a n c e [ i ] < = 1 0 5 1 <= distance[i] <= 10^5 1<=distance[i]<=105

From: LeetCode
Link: 335. Self Crossing

---

Solution:

Ideas:

1. Case 1: When the current move makes a cross with the move 2 steps before it.
2. Case 2: When the current move makes a cross by touching the line made 3 steps before.
3. Case 3: When the current move crosses by overlapping the line made 4 steps before.

Code:

bool isSelfCrossing(int* distance, int distanceSize) {
    if (distanceSize < 4) {
        return false;
    }
    
    for (int i = 3; i < distanceSize; i++) {
        // Case 1: Fourth line crosses the first line
        if (distance[i] >= distance[i - 2] && distance[i - 1] <= distance[i - 3]) {
            return true;
        }
        
        // Case 2: Fifth line meets the first line
        if (i >= 4 && distance[i - 1] == distance[i - 3] && distance[i] + distance[i - 4] >= distance[i - 2]) {
            return true;
        }
        
        // Case 3: Sixth line crosses the first line
        if (i >= 5 && distance[i - 2] >= distance[i - 4] && distance[i] + distance[i - 4] >= distance[i - 2] &&
            distance[i - 1] <= distance[i - 3] && distance[i - 1] + distance[i - 5] >= distance[i - 3]) {
            return true;
        }
    }
    
    return false;
}