Formatted question description: https://leetcode.ca/all/1232.html

1232. Check If It Is a Straight Line (Easy)

You are given an array coordinates, coordinates[i] = [x, y], where [x, y] represents the coordinate of a point. Check if these points make a straight line in the XY plane.

 

 

Example 1:

Input: coordinates = [[1,2],[2,3],[3,4],[4,5],[5,6],[6,7]]
Output: true

Example 2:

Input: coordinates = [[1,1],[2,2],[3,4],[4,5],[5,6],[7,7]]
Output: false

 

Constraints:

  • 2 <= coordinates.length <= 1000
  • coordinates[i].length == 2
  • -10^4 <= coordinates[i][0], coordinates[i][1] <= 10^4
  • coordinates contains no duplicate point.

Related Topics:
Array, Math, Geometry

Solution 1.

// OJ: https://leetcode.com/problems/check-if-it-is-a-straight-line/

// Time: O(N)
// Space: O(1)
class Solution {
public:
    bool checkStraightLine(vector<vector<int>>& A) {
        int N = A.size(), x1 = A[0][0], y1 = A[0][1], x2 = A[1][0], y2 = A[1][1];
        for (int i = 2; i < N; ++i) {
            if ((A[i][1] - y1) * (x2 - x1) != (y2 - y1) * (A[i][0] - x1)) return false;
        }
        return true;
    }
};

Java

class Solution {
    public boolean checkStraightLine(int[][] coordinates) {
        int length = coordinates.length;
        if (length == 2)
            return true;
        int deltaX = coordinates[1][0] - coordinates[0][0], deltaY = coordinates[1][1] - coordinates[0][1];
        for (int i = 2; i < length; i++) {
            int curDeltaX = coordinates[i][0] - coordinates[i - 1][0], curDeltaY = coordinates[i][1] - coordinates[i - 1][1];
            if (deltaX * curDeltaY != deltaY * curDeltaX)
                return false;
        }
        return true;
    }
}

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