汕头市队赛 C KMP codeforces B. Image Preview

汕头市队赛题目传送门

codeforces题目传送门

这道题我的做法是 尝试先往左走然后往右走 或者先往右走然后往左走 然后注意一下枚举顺序就okay啦

#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
using namespace std;
const int M=1e6+;
LL read(){
    LL ans=,f=,c=getchar();
    while(c<''||c>''){if(c=='-') f=-; c=getchar();}
    while(c>=''&&c<=''){ans=ans*+(c-''); c=getchar();}
    return ans*f;
}
int n,a,b,T;
LL w[M],ans;
char s[M];
LL pd1(int l,int r){
    LL sum=w[r]-w[l-];
    int now=(r-l)+(n+-l);
    return sum+(LL)now*a;
}
LL pd2(int l,int r){
    LL sum=w[r]-w[l-];
    int now=(r-l)+(r-n-);
    return sum+(LL)now*a;
}
int main()
{
    n=read(); a=read(); b=read(); T=read();
    scanf("%s",s+);
    for(int i=n+;i<=*n;i++) s[i]=s[i-n];
    for(int i=;i<=*n;i++) w[i]=(s[i]=='w'?(b+):)+w[i-];
//    for(int i=1;i<=2*n;i++) printf("%lld ",w[i]); printf("\n");
    int l=n+;
    for(int r=*n;r>=n+;r--){
        while(l>r-n+&&pd1(l-,r)<=T) l--;
        if(pd1(l,r)<=T) ans=max(ans,(LL)(r-l+));
    }
    //printf("%lld\n",ans);
    int r=n+;
    for(int l=;l<=n+;l++){
        while(r<l+n-&&pd2(l,r+)<=T) r++;
        if(pd2(l,r)<=T) ans=max(ans,(LL)(r-l+));
    }
//    ans=min(ans,(LL)n);
    printf("%lld\n",ans);
    return ;
}