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CSP 202006-1线性分类器python实现

 3 years ago
source link: http://www.cnblogs.com/pxsong/p/13582877.html
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思路

这题问题是对于这一群点和一条直线，我们也不知道直线上方的是A类还是直线下方的是A类。其实对于这个二分类问题，我们也没必要知道。 我们只需要判断直线每一测的点是不是一类（A类或B类）就可以了。

至于如何判断这一侧的点是不是一类，用一个set就可以了：把这一侧的点的自身类别（A或B）全都扔进一个set，如果是同一类，那么set的大小肯定是1。

进而，如果直线两侧对应的set大小全都是1，那么就二分类成功了。

代码

m, n = [int(i) for i in input().split()]

dict = {}
for i in range(m):
    line = input().split()
    x, y, s = line
    x, y = int(x), int(y)
    dict[(x, y)] = s

for i in range(n):
    aimsA = set()
    aimsB = set()
    line = input().split()
    a, b, c = [int (i) for i in line]
    for k, v in dict.items():
        x, y = k[0], k[1]
        if  a + b * x + c * y > 0:
            aimsA.add(v)
        else:
            aimsB.add(v)
    if len(aimsA) == 1 and len(aimsB) == 1:
        print("Yes")
    else:
        print("No")

report

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