Check If It Is a Straight Line

给一个数组, 里面是点, 问这些点在不在一个直线上. 这个题要用斜率公式算, y=ax+b, where (x,y) from array. 先用一组算出a, 然后再算b.

class Solution {
    public boolean checkStraightLine(int[][] c) {
        double s = (double)(c[1][1] - c[0][1]) / (c[1][0] - c[0][0]);
        double m = c[0][1] - s*c[0][0];
        for(int i = 2; i < c.length; i++) {
            int t = (int)(s * c[i][0] + m);
            if(t != c[i][1])
                return false;
        }
        return true;
    }
}