大数的加减乘除幂

title: 大数的加减乘除幂date: 2020-12-10 10:46
tags: C++
categories: 编程练习

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#include <iostream>
#include <string>
#include <stack>
#include <algorithm>  //reverse
using namespace std;
int main()
{
    string a,b;
    stack<int>result;
    cin>>a>>b;
    int i = 0;
    int add = 0,t = 0;
    reverse(a.begin(),a.end());  //倒置字符串 
    reverse(b.begin(),b.end());
    while(i < a.length() && i < b.length())
    {
        t = (a.at(i) + b.at(i) + add - 96);
        result.push(t%10);
        add = t/10;
        i++;
    }
    while(i < a.length())
    {
        t = (a.at(i) + add - 48);
        result.push(t%10);
        add = t/10;
        i++;
    }
    while(i < b.length())
    {
        t = (b.at(i) + add - 48);
        result.push(t%10);
        add = t/10;
        i++;
    }
    if(add) result.push(add); 
    while(!result.empty())
    {
        cout<<result.top();
        result.pop();
    }
    cout<<"\nDone!"<<endl;
    return 0;
}

*

#include <iostream>
#include <stack>
#include <string>
#include <algorithm>
using namespace std;
void add_string(string &r,string &a)
{
    string st = r;  //借助st实现result += temp 
    r.clear();      //result清空 
    int i = 0,add = 0,t;
    while(i < st.length() && i < a.length())
    {
        t = (st.at(i) + a.at(i) + add - 96);
        r += (t%10 +48);
        add = t/10;
        i++;
    }
    while(i < st.length())
    {
        t = (st.at(i) + add - 48);
        r += (t%10 +48);
        add = t/10;
        i++;
    }
    while(i < a.length())
    {
        t = (a.at(i) + add - 48);
        r += (t%10 +48);
        add = t/10;
        i++;
    }
    if(add) r += add+48;
    return;
}
int main()
{
    //calculate
    string result;
    string temp; 
    string a,b;
    cin >> a >> b;
    if(a.length() > b.length())
    {
        string t;
        t = a;
        a = b;
        b = t;
    }   //a 作为乘法中的较小数 
    reverse(a.begin(), a.end());
    reverse(b.begin(),b.end());
    int i = 0,j= 0,t = 0;
    int add = 0;
    int flag;
    while (i < a.length())
    {
        flag = i;
        while(flag--) temp += '0';
        for(j = 0; j < b.length(); j++)
        {
            t = (a.at(i)-48) * (b.at(j)-48) + add;
            temp += (t%10 + 48);
            add = t/10;
        }
        if(add) temp += add+48;
        add = 0;
        add_string(result,temp);
        temp.clear();
        i++;    
    }
    stack <int> st;
    for(i = 0;i < result.length();i++)
    {
        st.push(result.at(i) - 48);
    }
    while(!st.empty())
    {
        cout<<st.top();
        st.pop();
    }
    cout << "\nDone" << endl;
    return 0;
}