【BZOJ】1754: [Usaco2005 qua]Bull Math

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=100;

char s1[maxn],s2[maxn];
int a[maxn],b[maxn],c[maxn],lena,lenb,lenc;
int main(){
    scanf("%s%s",s1,s2);
    lena=strlen(s1);lenb=strlen(s2);
    for(int i=0;i<lena;i++)a[lena-i]=s1[i]-‘0‘;    
    for(int i=0;i<lenb;i++)b[lenb-i]=s2[i]-‘0‘;
    for(int i=1;i<=lena;i++){
        int x=0;
        for(int j=1;j<=lenb;j++){
            x=a[i]*b[j]+x+c[i+j-1];
            c[i+j-1]=x%10;
            x/=10;
        }
        c[i+lenb]=x;
    }
    lenc=lena+lenb;
    while(lenc>1&&!c[lenc])lenc--;
    for(int i=lenc;i>=1;i--)printf("%d",c[i]);
    return 0;
}