cf 762C. Two strings

因为要删去1个串（读错题），所以就直接二分搞就好了。

需要预处理出2个分别从头到尾，或从尾到头需要多长a串的数组，然后二分删去多长就好了。

#include<bits/stdc++.h> 
#define LL long long 
#define N 100005
#define lowbit(x) x&(-x)
using namespace std;
inline int ra()
{
    int x=0,f=1; char ch=getchar();
    while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
char a[N], b[N];
int fl[N], fr[N];
int la, lb, i, j, mid, l, r, a1, a2;
int main()
{
    scanf("%s%s",a+1,b+1);
    la=strlen(a+1); lb=strlen(b+1);
    for (i=1,fl[0]=j=0; b[i]; i++)
    {
        for (j++; j<=la && a[j]!=b[i]; j++);
        fl[i]=j; 
    }
    for (i=lb, fr[lb+1]=j=la+1; b[i]; i--)
    {
        for (j--; j>0 && a[j]!=b[i]; j--);
        fr[i]=j;
    }
    for (l=0,r=lb; l<=r;)
    {
        mid=(l+r)>>1;
        for (i=0; i+mid<=lb; i++)
            if (fl[i]<fr[i+mid+1]) break;
        if (i+mid<=lb) a1=i,a2=mid+i+1,r=mid-1;
        else l=mid+1;
    }
    for (int i=1; i<=a1; i++) putchar(b[i]);
    for (int i=a2; i<=lb; i++) putchar(b[i]);
    if (a2-a1>lb) putchar('-');
    return 0;
}