[Leetcode 1037] Valid Boomerang

原题说明

A boomerang is a set of 3 points that are all distinct and not in a straight line.

Given a list of three points in the plane, return whether these points are a boomerang.

Example 1:

Input: [[1,1],[2,3],[3,2]]
Output: true

Example 2:

Input: [[1,1],[2,2],[3,3]]
Output: false

Note:

points.length == 3
points[i].length == 2
0 <= points[i][j] <= 100

解题思路

判断AB，AC斜率是否相同，如果相同则在一条线上
注意用乘法好过除法, 因为不用判断分母为0了。
面试时要考虑特殊情况，比如两个点重合是否算同线 (本题是distinct的点，所以不用考虑)

示例代码 (cpp)

class Solution {
public:
    bool isBoomerang(vector<vector<int>>& points) {
        return (points[0][0] - points[1][0]) * (points[0][1] - points[2][1]) != (points[0][0] - points[2][0]) * (points[0][1] - points[1][1]);
    }
};

示例代码 (java)

class Solution {
    public boolean isBoomerang(int[][] p) {
        return (p[0][0] - p[1][0]) * (p[0][1] - p[2][1]) != (p[0][0] - p[2][0]) * (p[0][1] - p[1][1]);
    }
}

示例代码 (python)

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class Solution:
    def isBoomerang(self, points: List[List[int]]) -> bool:
        return (points[0][0] - points[1][0]) * (points[0][1] - points[2][1]) != (points[0][0] - points[2][0]) * (points[0][1] - points[1][1])

复杂度分析

时间复杂度: O(1)
空间复杂度: O(1)

归纳总结

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