[codeforces 1293A] ConneR and the A.R.C. Markland-N 不超时的二分/无限长数组map+桶排序

[codeforces 1293A] ConneR and the A.R.C. Markland-N 不超时的二分/无限长数组map+桶排序

总目录详见https://blog.csdn.net/mrcrack/article/details/103564004

在线测评地址https://codeforces.com/contest/1293/problem/A

方法一：不超时的二分

Problem	Lang	Verdict	Time	Memory
A - ConneR and the A.R.C. Markland-N	GNU C++11	Accepted	31 ms	0 KB

//想不到，写了二分，写得不好，还会超时

#include <cstdio>
#include <algorithm>
#define N 1010
using namespace std;
int a[N],k;
int bisection(int x){//返回1找到,返回0没找到
	int left=0,right=k+1,mid;
	while(left+1<right){
		mid=(left+right)/2;
		if(a[mid]<x)left=mid;
		else if(a[mid]>x)right=mid;
		else if(a[mid]==x)return 1;//此句关键，及时结束二分搜索，也是不超时的关键所在。
	}
	return 0;
}
int main(){
	int t,n,s,i,j,step;
	scanf("%d",&t);
	while(t--){
		scanf("%d%d%d",&n,&s,&k);
		step=0;
		for(i=1;i<=k;i++)scanf("%d",&a[i]);
		a[0]=a[k+1]=0;
		sort(a+1,a+1+k);
		while(1){
			if(s+step<=n&&bisection(s+step)==0)break;
			else if(s-step>0&&bisection(s-step)==0)break;
			step++;
		}
		printf("%d\n",step);
	}
	return 0;
}

方法二：无限长数组map+桶排序

Problem	Lang	Verdict	Time	Memory
A - ConneR and the A.R.C. Markland-N	GNU C++11	Accepted	31 ms	0 KB

#include <cstdio>
#include <map>
#define N 1010
using namespace std;
int a,k;
int main(){
	int t,n,s,i,j,step;
	scanf("%d",&t);
	while(t--){
		map<int,int> used;
		scanf("%d%d%d",&n,&s,&k);
		step=0;
		for(i=1;i<=k;i++)scanf("%d",&a),used[a]=1;
		while(1){
			if(s+step<=n&&used[s+step]==0)break;
			else if(s-step>0&&used[s-step]==0)break;
			step++;
		}
		printf("%d\n",step);
	}
	return 0;
}