【Educational Codeforces Round 53 (Rated for Div. 2) C】Vasya and Robot

【链接】 我是链接,点我呀:)

【题意】

【题解】

如果|x|+|y|>n
显然。从(0,0)根本就没法到(x,y)
但|x|+|y|

【代码】

#include <bits/stdc++.h>
#define ll long long
#define rep1(i,a,b) for (int i = a;i <= b;i++)
#define rep2(i,a,b) for (int i = a;i >= b;i--)
using namespace std;

const int N = 2e5;

int n;
ll x,y;
ll px[N+10],py[N+10];
char s[N+10];

bool ok(int len){
	rep1(i,1,n){
		if (i+len-1>n) return 0;
	 	ll x0 = px[i-1]-px[0],y0=py[i-1]-py[0];
	 	x0+=px[n]-px[i+len-1];y0+=py[n]-py[i+len-1];
	 	ll temp = abs(x-x0)+abs(y-y0);
	 	if (temp<=len) return 1;
	}
	return 0;
}

int main(){
	#ifdef ccy
			freopen("rush.txt","r",stdin);
	#endif
	scanf("%d",&n);
	scanf("%s",s+1);
	scanf("%lld%lld",&x,&y);
	ll temp = abs(x)+abs(y);
	if (temp>n || ( (temp&1) != (n&1) ) ){
		puts("-1");
		return 0;
	}
	rep1(i,1,n){
		px[i] = px[i-1];py[i] = py[i-1];
	 	if (s[i]=='L') px[i]--;
	 	if (s[i]=='R') px[i]++;
	 	if (s[i]=='U') py[i]++;
	 	if (s[i]=='D') py[i]--;
	}
	int l = 0,r = n,temp1 = -1;
	while (l <= r){
		int mid = (l+r)>>1;
		if (ok(mid)){
		 	temp1 = mid;
		 	r = mid-1;
		}else{
		 	l = mid+1;
		}
	}
	printf("%d\n",temp1);
 	return 0;
}