【csp模拟赛九】--dfs

思路：

　　这道题可以宽搜，深搜，最短路

代码：

#include<cstdio>
#include<cstring>
#include<iostream>
#include<queue>
using namespace std;
queue<pair<int,int> > q;
int n,m,c[25],s;
long long f[25][1010],ans;
bool v[25][1010];
int Abs(int x)
{
	return x >= 0 ? x : -x;
}
void bfs()
{
	q.push(make_pair(s,1));
	v[s][1] = 1;	f[s][1] = 0;
	while(!q.empty())
	{
		int x = q.front().first;
		int y = q.front().second;
		q.pop();	v[x][y] = 0;
		for(int i = 1;i <= m;i ++)
		{
			int em = y + c[i];
			if(em <= n && em >= 1)
			{
				if(f[i][em] > f[x][y] + Abs(i - x) + Abs(2 * c[i]))
				{
					f[i][em] = f[x][y] + Abs(i - x) + Abs(2 * c[i]);
					if(!v[i][em])	q.push(make_pair(i,em)),v[i][em] = 1;
				}
			}
		}
	}
}
int main()
{
	freopen("elevator.in","r",stdin);
	freopen("elevator.out","w",stdout);
	scanf("%d%d",&n,&m);
	for(int i = 1;i <= m;i ++)
	{
		scanf("%d",&c[i]);
		if(c[i] == 0)	s = i;
	}
	memset(f,0x3f,sizeof(f));
	ans = f[0][0];	
	bfs();
	for(int i = 1;i <= m;i ++)	ans = min(ans,f[i][n]);
	if(ans != f[0][0])	printf("%d\n",ans);
	else	printf("-1\n");
	fclose(stdin);
	fclose(stdout);
	return 0;
}
/*
6 3
-1 0 2
*/