题解 | #大数乘法#

#include <algorithm>
#include <iterator>
#include <string>
#include <vector>
class Solution {
public:

    string solve(string s, string t) {
        int n = s.size(), m = t.size();
        vector<int> v(n+m);
        reverse(s.begin(),s.end());
        reverse(t.begin(),t.end());
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<m;j++)
            {
                v[i+j] += (s[i]-'0') * (t[j]-'0');
                
            }
        }
        int count = 0;
        string ret;
        for(auto x : v)
        {
            x += count;
            ret += x%10 + '0';
            count = x / 10; 
        }
        if(count)
        {
            ret += count - '0';
        }
        while(ret.size()>1 && ret.back() == '0') ret.pop_back();
        reverse(ret.begin(),ret.end());

        return ret;
        
    }
};