cf1073c 二分+二维前缀和

#include<bits/stdc++.h>
using namespace std;
#define maxn 200005
char s[maxn];
int tmp,n,x,y,sum[][maxn];
map<char,int>mp;

int judge(int mid){//能否在mid长度内修改完
    for(int l=;l+mid-<=n;l++){
        int r=l+mid-;
        int Y=sum[][n]-sum[][r]+sum[][l-];
        int X=sum[][n]-sum[][r]+sum[][l-];
        int tot=abs(x-X)+abs(y-Y);//在区间[l,r]要走的距离
        if(tot<=mid)return ;
    }
    return ;
}

int main(){
    mp['U']=,mp['D']=-,mp['L']=-,mp['R']=;
    cin>>n>>s+>>x>>y;
    tmp=abs(x)+abs(y);
    if(n<tmp || tmp%!=n%){
        puts("-1");
        return ;
    }

    for(int i=;i<=n;i++){
        if(s[i]=='U'||s[i]=='D'){
            sum[][i]=sum[][i-]+mp[s[i]];
            sum[][i]=sum[][i-];
        }
        else {
            sum[][i]=sum[][i-];
            sum[][i]=sum[][i-]+mp[s[i]];
        }
    }

    int ans=-,l=,r=n,mid;
    while(l<=r){
        mid=l+r>>;
        if(judge(mid))
            ans=mid,r=mid-;
        else l=mid+;
    }
    printf("%d\n",ans);
}