English
1232. Check If It Is a Straight Line 
Problem Statement:
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.
Solution:
java
/*
* slope = tan0 = (x - x1) / (y - y1)
* for line being straight line,
* slope b/w every two points must be equal, i.e.
* (x - x1) / (y - y1) = (x1 - x0) / (y1 - y0)
*/
public boolean checkStraightLine(int[][] coordinates) {
if (coordinates.length == 2)
return true;
int x0 = coordinates[0][0], y0 = coordinates[0][1],
x1 = coordinates[1][0], y1 = coordinates[1][1];
int dx = x1 - x0,
dy = y1 - y0;
for (int[] coordinate : coordinates) {
int x = coordinate[0], y = coordinate[1];
if (dx * (y - y1) != dy * (x - x1))
return false;
}
return true;
}
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