字首和思想

https://blog.csdn.net/chen_yuazzy/article/details/77074410

#include<cstdio>
#include<cstring>
#define m 300000
using namespace std;
char a[m];
char b[m];
int pre0[m];
int pre1[m];
int main()
{
    int len1,len2,i;
    long long s=0;
    gets(a);
    gets(b);
    len1=strlen(a);
    len2=strlen(b);
    for(i=0;i<len2;i++)
    {
        if(b[i]=='0') {
                pre0[i]=pre0[i-1]+1;
                pre1[i]=pre1[i-1];
        }
        else if(b[i]=='1') {
                pre1[i]=pre1[i-1]+1;
                pre0[i]=pre0[i-1];
        }
    }
    for(i=0;i<len1;i++)
    {
        if(a[i]=='0')
        {
            s+=pre1[i+len2-len1]-pre1[i-1];
        }
        else if(a[i]=='1')
        {
            s+=pre0[i+len2-len1]-pre0[i-1];
        }
    }
    printf("%lld",s);
    return 0;
}