POJ 3009 Curling 2.0 DFS

读懂题意就能写了，递归层数最多10，怎么写都能过。

DFS：

//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<sstream>
#include<cmath>
#include<climits>
#include<string>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define pb(a) push(a)
#define INF 0x1f1f1f1f
#define lson idx<<1,l,mid
#define rson idx<<1|1,mid+1,r
#define PI  3.1415926535898
template<class T> T min(const T& a,const T& b,const T& c) {
    return min(min(a,b),min(a,c));
}
template<class T> T max(const T& a,const T& b,const T& c) {
    return max(max(a,b),max(a,c));
}
void debug() {
#ifdef ONLINE_JUDGE
#else

    freopen("in.txt","r",stdin);
    //freopen("d:\out1.txt","w",stdout);
#endif
}
int getch() {
    int ch;
    while((ch=getchar())!=EOF) {
        if(ch!=' '&&ch!='
')return ch;
    }
    return EOF;
}

const int maxn=25;
int g[maxn][maxn];
int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};
int n,m;
int res;
int dfs(int x,int y,int t)
{
    for(int d=0;d<4;d++)
    {
        int nx=x+dx[d],ny=y+dy[d];
        if(nx<1||nx>n||ny<1||ny>m||g[nx][ny]==1)
                continue;
        for(;;)
        {
            if(nx<1||nx>n||ny<1||ny>m)
                break;

            if(g[nx][ny]==3)
            {
                res=min(res,t);
                return 0;
            }
            if(g[nx][ny]==1)
            {
                if(t<10)
                {
                    g[nx][ny]=0;
                    dfs(nx-dx[d],ny-dy[d],t+1);
                    g[nx][ny]=1;
                }

                break;
            }
            nx+=dx[d];
            ny+=dy[d];
        }
    }
}

int main()
{
    while(scanf("%d%d",&m,&n)!=EOF&&n)
    {
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                scanf("%d",&g[i][j]);
        res=INF;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(g[i][j]==2)
                {
                    g[i][j]=0;
                    dfs(i,j,1);
                }
        printf("%d
",res==INF?-1:res);
    }
    return 0;
}

迭代加深速度会快一点：

//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<sstream>
#include<cmath>
#include<climits>
#include<string>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define pb(a) push(a)
#define INF 0x1f1f1f1f
#define lson idx<<1,l,mid
#define rson idx<<1|1,mid+1,r
#define PI  3.1415926535898
template<class T> T min(const T& a,const T& b,const T& c) {
    return min(min(a,b),min(a,c));
}
template<class T> T max(const T& a,const T& b,const T& c) {
    return max(max(a,b),max(a,c));
}
void debug() {
#ifdef ONLINE_JUDGE
#else

    freopen("in.txt","r",stdin);
    //freopen("d:\out1.txt","w",stdout);
#endif
}
int getch() {
    int ch;
    while((ch=getchar())!=EOF) {
        if(ch!=' '&&ch!='
')return ch;
    }
    return EOF;
}

const int maxn=25;
int g[maxn][maxn];
int dx[]={0,0,1,-1};
int dy[]={1,-1,0,0};
int n,m;

int dfs(int x,int y,int t,int limit)
{
    for(int d=0;d<4;d++)
    {
        int nx=x+dx[d],ny=y+dy[d];
        if(nx<1||nx>n||ny<1||ny>m||g[nx][ny]==1)
                continue;
        for(;;)
        {
            if(nx<1||nx>n||ny<1||ny>m)
                break;

            if(g[nx][ny]==3)
            {
                return 1;
            }
            if(g[nx][ny]==1)
            {
                if(t<limit)
                {
                    g[nx][ny]=0;
                    if(dfs(nx-dx[d],ny-dy[d],t+1,limit))return 1;
                    g[nx][ny]=1;
                }

                break;
            }
            nx+=dx[d];
            ny+=dy[d];
        }
    }
    return 0;
}

int main()
{
    while(scanf("%d%d",&m,&n)!=EOF&&n)
    {
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                scanf("%d",&g[i][j]);
        int res=INF;
        for(int i=1;i<=n;i++)
            for(int j=1;j<=m;j++)
                if(g[i][j]==2)
                {
                    g[i][j]=0;
                    for(int limit=1;limit<=10;limit++)
                        if(dfs(i,j,1,limit))
                        {
                            res=limit;
                            break;
                        }
                }
        printf("%d
",res==INF?-1:res);
    }
    return 0;
}