[Leetcode] Multiply Strings

最新推荐文章于 2022-05-13 12:53:03 发布

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本文介绍了一种使用C++实现的两个大整数相乘的方法。这些大整数以字符串形式表示，通过逐位相乘并累加的方式进行计算。此方法适用于处理任意精度的大数运算。

Given two numbers represented as strings, return multiplication of the numbers as a string.

Note: The numbers can be arbitrarily large and are non-negative.

class Solution {
public:
    string multiply(string num1, string num2) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function        
        int size1 = num1.size();
        int size2 = num2.size();
        
        vector<int> result(size1+size2,0);
        
        for(int i=0;i<size1;i++)
        {
            int carry = 0;
            int n1 = num1[size1-i-1]-'0'; 
            for(int j=0;j<size2;j++)
            {
                int n2 = num2[size2-j-1]-'0';
                carry = n1*n2 + carry + result[i+j];
                result[i+j] = carry%10;
                carry = carry/10;            
            }            
            result[i+size2] = carry;
        }
        
         int i = size1 + size2 - 1;  
         while( i>0 && result[i]==0) i--;
         string ans;
         ans = "";
         
         while(i>=0)
         {
             ans += char(result[i]+'0');
             i--;             
         }
         
         return ans; 
    }
};