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Formatted question description: https://leetcode.ca/all/537.html
537. Complex Number Multiplication (Medium)
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 integer a and b will both belong to the range of [-100, 100]. And the output should be also in this form.
Solution 1.
// OJ: https://leetcode.com/problems/complex-number-multiplication/
// Time: O(N)
// Space: O(N)
class Solution {
private:
vector<int> parse(string &s) {
vector<int> ans(2, 0);
ans[0] = stoi(s);
int i = s.find_first_of("+");
ans[1] = stoi(s.substr(i + 1));
return ans;
}
public:
string complexNumberMultiply(string a, string b) {
auto m = parse(a), n = parse(b);
int x = m[0] * n[0] - m[1] * n[1], y = m[1] * n[0] + m[0] * n[1];
return to_string(x) + "+" + to_string(y) + "i";
}
};
Java
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class Solution { public String complexNumberMultiply(String a, String b) { int aReal = Integer.parseInt(a.substring(0, a.indexOf('+'))); int aImag = Integer.parseInt(a.substring(a.indexOf('+') + 1, a.indexOf('i'))); int bReal = Integer.parseInt(b.substring(0, b.indexOf('+'))); int bImag = Integer.parseInt(b.substring(b.indexOf('+') + 1, b.indexOf('i'))); int mulReal = aReal * bReal - aImag * bImag; int mulImag = aReal * bImag + bReal * aImag; return mulReal + "+" + mulImag + "i"; } }
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// OJ: https://leetcode.com/problems/complex-number-multiplication/ // Time: O(N) // Space: O(N) class Solution { private: vector<int> parse(string &s) { vector<int> ans(2, 0); ans[0] = stoi(s); int i = s.find_first_of("+"); ans[1] = stoi(s.substr(i + 1)); return ans; } public: string complexNumberMultiply(string a, string b) { auto m = parse(a), n = parse(b); int x = m[0] * n[0] - m[1] * n[1], y = m[1] * n[0] + m[0] * n[1]; return to_string(x) + "+" + to_string(y) + "i"; } };
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class Solution: def complexNumberMultiply(self, num1: str, num2: str) -> str: a, b = map(int, num1[:-1].split('+')) c, d = map(int, num2[:-1].split('+')) return f'{a * c - b * d}+{a * d + c * b}i' ############ class Solution(object): def complexNumberMultiply(self, a, b): """ :type a: str :type b: str :rtype: str """ (ar, ac), (br, bc) = map(int, a[:-1].split("+")), map(int, b[:-1].split("+")) return "{}+{}i".format(str(ar * br - ac * bc), str(ar * bc + br * ac))