C :

#include <stdlib.h>
#include <stdio.h>
 
char a[9][9];
int n,m,t,dx,dy,f;
int g[4][2]= {{1,0},{0,1},{-1,0},{0,-1}};
void dfs(int x,int y,int p)
{
    int i,sx,sy,s;
    s=p-abs(x-dx)-abs(y-dy);
    if(x>n||y>m||x<=0||y<=0) return;
    if(p==0&&s==0) f=1;
    if(f) return;
    if(s<0||s&1) return;
    for(i=0; i<4; i++)
    {
        sx=x+g[i][0];
        sy=y+g[i][1];
        if(a[sx][sy]!='X')
        {
            a[sx][sy]='X';
            dfs(sx,sy,p-1);
            a[sx][sy]='.';
        }
    }
    return;
}
int main()
{
    int i,j,x,y,b;
    while(scanf("%d%d%d",&n,&m,&t)&&(n!=0||m!=0||t!=0))
    {
        getchar();
        b=0;
        for(i=1; i<=n; i++)
        {
            for(j=1; j<=m; j++)
            {
                scanf("%c",&a[i][j]);
                if(a[i][j]=='S')
                {
                    x=i;
                    y=j;
                }
                else if(a[i][j]=='D')
                {
                    dx=i;
                    dy=j;
                }
                else if(a[i][j]=='X') b++;
            }
            getchar();
        }
 
        if(n*m-b<=t)
        {
            printf("NO\n");
            continue;
        }
        f=0;
        a[x][y]='X';
        dfs(x,y,t);
        if(f) printf("YES\n");
        else printf("NO\n");
    }
    return 0;
}
 
/**************************************************************
    Problem: 1056
    User: admin
    Language: C
    Result: 正确
    Time:2 ms
    Memory:1064 kb
****************************************************************/

C++ :

#include <stdio.h>
int n,m,t,ok;
char a[11][11]; 
void dd(int t,int x,int y)
{
	if((t==0)&&(a[x][y]=='D'))
		ok=1;
	if(t==0)
		return;
	if(ok==1)
		return;
	if((a[x-1][y]=='.')||((a[x-1][y]=='D')&&(t==1)))
	{
		a[x][y]='X';
		dd(t-1,x-1,y);
		a[x][y]='.';
	}
	if((a[x+1][y]=='.')||((a[x+1][y]=='D')&&(t==1)))
	{
		a[x][y]='X';
		dd(t-1,x+1,y);
		a[x][y]='.';
	}
	if((a[x][y-1]=='.')||((a[x][y-1]=='D')&&(t==1)))
	{
		a[x][y]='X';
		dd(t-1,x,y-1);
		a[x][y]='.';
	}
	if((a[x][y+1]=='.')||((a[x][y+1]=='D')&&(t==1)))
	{
		a[x][y]='X';
		dd(t-1,x,y+1);
		a[x][y]='.';
	}
}
int run()
{
	int i,j,x,y;
	char s[10];
	for(i=0;i<=n+1;i++)
		for(j=0;j<=m+1;j++)
			a[i][j]='X';
	for(i=1;i<=n;i++)
	{
		scanf("%s",s);
		for(j=1;j<=m;j++)
		{
			a[i][j]=s[j-1];
			if(a[i][j]=='S')
			{
				x=i;
				y=j;
			}
		}
	}
	ok=0;
	dd(t,x,y);
	if(ok==1)
		printf("YES\n");
	else
		printf("NO\n");
}
int main()
{
	scanf("%d%d%d",&n,&m,&t);
	while(n!=0)
	{
		run();
		scanf("%d%d%d",&n,&m,&t);
	}
	return 0;
}

Python :

def space_input(p=''):
    s=raw_input(p).split()
    for i in range(len(s)):
        s[i]=eval(s[i])
    return tuple(s)
class Mymap:
    def __init__(self,h,w):
        self.sx=self.sy=0
        self.height=h
        self.width=w
        self.allmoves=set()
        self.maze=[[' ' for i in range(w)] for i in range(h)]
    def getmap(self):
        for i in range(self.height):
            line=raw_input()
            for j in range(self.width):
                self.maze[i][j]=line[j]
                if line[j]=='S':
                    self.sx,self.sy=i,j
    def move(self,maze,sx,sy,moves=0):
        if maze[sx][sy]=='D':
            self.allmoves.add(moves)
        else:
            new=eval(repr(maze))
            new[sx][sy]='X'
            for i,j in [(sx-1,sy),(sx+1,sy),(sx,sy-1),(sx,sy+1)]:
                if 0<=i<self.height and 0<=j<self.width and new[i][j]!='X':
                    self.move(new,i,j,moves+1)
h,w,t=space_input()
while h or w or t:
    a=Mymap(h,w)
    a.getmap()
    a.move(a.maze,a.sx,a.sy)
    if t in a.allmoves:
        print 'YES'
    else:
        print 'NO'
    h,w,t=space_input()