Ac日记——大整数减法 openjudge 1.6 11

#include<set>
#include<map>
#include<cmath>
#include<stack>
#include<queue>
#include<cstdio>
#include<string>
#include<vector>
#include<cstring>
#include<iostream>
#include<algorithm>

using namespace std;

char s1[221],s2[221];

void exchange()
{
    int l=0,r=strlen(s1)-1;
    while(r>l)
    {
        if(s1[l]>=‘0‘) s1[l]-=‘0‘;
        if(s1[r]>=‘0‘) s1[r]-=‘0‘;
        swap(s1[l],s1[r]);
        l++,r--;
    }
    if(l==r) s1[l]-=‘0‘;
    l=0,r=strlen(s2)-1;
    while(r>l)
    {
        if(s2[l]>=‘0‘) s2[l]-=‘0‘;
        if(s2[r]>=‘0‘) s2[r]-=‘0‘;
        swap(s2[l],s2[r]);
        l++,r--;
    }
    if(l==r) s2[l]-=‘0‘;
}

int main()
{
    cin>>s1;
    cin>>s2;
    exchange();
    //cout<<s1<<endl<<s2<<endl;
    for(int i=0;i<=219;i++)
    {
        if(s1[i]-s2[i]<0) s1[i+1]--,s1[i]+=10;
        s1[i]-=s2[i];
    }
    bool if_zero=true;
    for(int i=219;i>=0;i--)
    {
        if(s1[i]==0) continue;
        if_zero=false;
        for(int j=i;j>=0;j--) putchar(s1[j]+‘0‘);
        break;
    }
    if(if_zero) putchar(‘0‘);
    return 0;
}