实现两个字符串的乘法

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实现两个由数字构成的字符串的乘法，其实现代码如下所示：

#include<iostream>#include<string>#include<vector>using namespace std;string multiply(string &num1, string &num2){if (num1 == "0" || num2 == "0"){return "0";}int len1 = num1.length();int len2 = num2.length();vector<int> result(len1 + len2 - 1, 0);string resultStr = "";for (int i = len1 - 1; i >= 0; --i){for (int j = len2 - 1; j >= 0; --j){result[i + j] += (num1[i] - '0')*(num2[j] - '0');//关键的一步，两个位数和相等的乘积放在同一个地方}}string temp1, temp2;int k = len1 + len2 - 2;while (k != 0){temp1 = result[k] % 10 + '0';resultStr = temp1 + resultStr;result[k - 1] += result[k] / 10;--k;}temp1 = result[0] % 10 + '0';resultStr = temp1 + resultStr;if (result[0] >= 10){temp2 = result[0] / 10 + '0';resultStr = temp2 + resultStr;}return resultStr;}int main(){string s1 = "9";string s2 = "9";string s3 = "12564875421475";string s4 = "4578124754157841541";cout << "s1*s2 = " << multiply(s1, s2) << endl;cout << "s3*s4 = " << multiply(s3, s4) << endl;system("pause");return 0;}

实验结果如下所示：

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