537. Complex Number Multiplication

最新推荐文章于 2018-05-28 15:39:07 发布

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最新推荐文章于 2018-05-28 15:39:07 发布

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分类专栏：字符串

本文链接：https://blog.youkuaiyun.com/u013527178/article/details/79252201

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本文介绍了一种通过解析字符串形式的复数，并实现其乘法运算的方法。利用C++标准库中的stringstream和字符串操作函数，从输入字符串中提取出复数的实部和虚部，完成乘法运算并返回字符串形式的结果。

Given two strings representing two complex numbers.

You need to return a string representing their multiplication. Note i² = -1 according to the definition.

Example 1:

Input: "1+1i", "1+1i"
Output: "0+2i"
Explanation: (1 + i) * (1 + i) = 1 + i² + 2 * i = 2i, and you need convert it to the form of 0+2i.

Example 2:

Input: "1+-1i", "1+-1i"
Output: "0+-2i"
Explanation: (1 - i) * (1 - i) = 1 + i² - 2 * i = -2i, and you need convert it to the form of 0+-2i.

Note:

The input strings will not have extra blank.
The input strings will be given in the form of a+bi, where the integera and b will both belong to the range of [-100, 100]. Andthe output should be also in this form.

思路：提取出实部与虚部

知识点：1.字符转整形；2.在string中提取整数

代码1：

class Solution {
public:
    string complexNumberMultiply(string a, string b) {
        int i=0,len=0,a1,a2,b1,b2;
        string sub;
        i = a.find("+");
        len = a.size();
        a1 = stoi(a.substr(0,i));
        a2 = stoi(a.substr(i+1,len-1));
        i = b.find("+");
        len = b.size();
        b1 = stoi(b.substr(0,i));
        b2 = stoi(b.substr(i+1,len-1));
        return (to_string(a1*b1-a2*b2)+"+"+to_string(a1*b2+a2*b1)+"i");
        
    }
};

string.find; string.substring; stoi（此处有问题）; to_string

代码2：

class Solution {
public:
    string complexNumberMultiply(string a, string b) {
        int ra, ia, rb, ib;
        char buff;
        stringstream aa(a), bb(b), ans;
        aa >> ra >> buff >> ia >> buff;
        bb >> rb >> buff >> ib >> buff;
        ans << ra*rb - ia*ib << "+" << ra*ib + rb*ia << "i";
        return ans.str();
    }
};

核心在于如何利用stringstream从字符串中提取数字。

http://www.cplusplus.com/reference/sstream/stringstream/

http://blog.youkuaiyun.com/sophia1224/article/details/53054698

https://www.cnblogs.com/hujunzheng/p/5042068.html