2736大整数减法，3180 整数减法

转载请注明出处：http://www.cnblogs.com/zhishoumuguinian/p/8430498.html

 

9999999999999999999999999999999999999                         
9999999999999

9999
4567
0
1

样例输出

9999999999999999999999990000000000000

5432
-1

#include<bits/stdc++.h>
#include<string>
using namespace std;

int main()
{
    string s1, s2;
    while(cin>>s1>>s2)
    {
        int a[250]= {0}, b[250]= {0};
        a[0]=s1.length();
        b[0]=s2.length();
        int i;
        for(i=1; i<=a[0]; i++)
        {
            a[i]=s1[a[0]-i]-'0';
        }
        for(i=1; i<=b[0]; i++)
        {
            b[i]=s2[b[0]-i]-'0';
        }
        int flag=0;
        for(i=max(a[0],b[0]); i>0; i--)
        {
            if(a[i]>b[i])
            {
                flag=1;
                break;
            }
            if(a[i]<b[i])
            {
                flag=-1;
                break;
            }
        }

        if(flag==0)
        {
            memset(a,0,sizeof(a));
            a[0]=1;
        }
        if(flag==1)
        {
            for(i=1; i<=a[0]; i++)
            {
                if(a[i]<b[i])
                {
                    a[i+1]--;
                    a[i]+=10;
                }
                a[i]-=b[i];
            }
            while(a[a[0]]==0)
                a[0]--;
        }
        if(flag==-1)
        {
            for(i=1; i<=b[0]; i++)
            {
                if(b[i]<a[i])
                {
                    b[i+1]--;
                    b[i]+=10;
                }
                a[i]=b[i]-a[i];
            }
            a[0]=b[0];
            while(a[a[0]]==0)
                a[0]--;
        }
        if(flag==-1)
            cout<<"-";
        for(i=a[0]; i>0; i--)
        {
            cout<<a[i];
        }
        cout<<endl;
    }
    return 0;
}