记录pat甲级做题中遇到的一些坑(JAVA)

1002 A+B for Polynomials (25)（25 分）

    This time, you are supposed to find A+B where A and B are two polynomials.
    Input

    Each input file contains one test case. Each case occupies 2 lines, and each line contains the information of a polynomial: K N1 a~N1~ N2 a~N2~ ... NK a~NK~, where K is the number of nonzero terms in the polynomial, Ni and a~Ni~ (i=1, 2, ..., K) are the exponents and coefficients, respectively. It is given that 1 <= K <= 10，0 <= NK < ... < N2 < N1 <=1000.

    Output

    For each test case you should output the sum of A and B in one line, with the same format as the input. Notice that there must be NO extra space at the end of each line. Please be accurate to 1 decimal place.

    Sample Input

    2 1 2.4 0 3.2
    2 2 1.5 1 0.5
    Sample Output

    3 2 1.5 1 2.9 0 3.2
乍看这道题很简单,放进map一顿乱揍就行了,结果首次提交答案是部分正确.仔细观看题意:要求保留一位小数.但是参数都是最多1位小数,怎么会出现不是一位小数的情况呢?(float a = 0; float b = 0; float c= a+b; c输出为0.0)
仔细想想,对了,计算机计算加减法的时候是采取的二进制补码计算的,所以二进制并不能精确表示十进制,所以计算的时候会出现一些差错的.会带一个小尾巴,比如0.10000000001