【uva】225 - Golygons（dfs有坑）
dfs的路径问题，毕竟坑的是一条路线不能走相同的转弯点，一开始BFS做的存状态超时，之后回溯dfs过的。
感觉没什么难度。
这个是TEL的BFS代码：
| 13970312 | 225 | Golygons | Time limit exceeded | C++ | 3.000 | 2014-07-31 09:42:55 |
#include <vector>
#include <list>
#include <map>
#include <string>
#include <set>
#include <cstring>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
#define MAXD 1000
#define LEN 300
int n;
int Map[MAXD][MAXD] = {0};
int dir[4][2] = {{1,0},{-1,0},{0,1},{0,-1}}; /*向右走，向左走，向上走，向下走*/
int dir_[2][2][2] = {{{0,1},{0,-1}},{{1,0},{-1,0}}};
char const _dir[] = "ewns";
/*0 1 2 3 分别代表向上，向下，向右，向左*/
struct State{
vector<int>rote; /*路线*/
int now_dir; /*当前方向*/
int step; /*当前要走第几步*/
int x,y; /*当前位置*/
};
bool can_move(int from_x,int from_y,int to_x,int to_y){
/*判断能否从(from_x,from_y) 走到 (to_x,to_y) */
if(from_x == to_x){
int t1 = min(from_y,to_y);
int t2 = max(from_y,to_y);
for(int i = t1 ; i <= t2 ; i++){
if(Map[to_x][i])
return false;
}
}
else if(from_y == to_y){
int t1 = min(from_x,to_x);
int t2 = max(from_x,to_x);
for(int i = t1 ; i <= t2 ; i++){
if(Map[i][to_y])
return false;
}
}
return true;
}
void bfs(){
queue<State>q;
for(int i = 0 ; i < 4 ; i++){ /*起始点*/
int _x = LEN + dir[i][0];
int _y = LEN + dir[i][1];
if(!Map[_x][_y]){ /*不是障碍*/
State start;
start.rote.push_back(i);
start.step = 2;
start.now_dir = i;
start.x = _x;
start.y = _y;
q.push(start);
}
}
int cnt = 0;
while(!q.empty()){
State s = q.front(); q.pop();
if(s.step == n + 1){
cnt ++;
for(int i = 0 ; i < s.rote.size(); i++)
printf("%c",_dir[s.rote[i]]);
printf("\n");
continue;
}
int k;
int step = s.step;
if(s.now_dir == 0 || s.now_dir == 1)
k = 0;
else
k = 1;
for(int i = 0; i < 2 ; i++){ /*每次只能转90度的弯*/
int _x = s.x + step * dir_[k][i][0];
int _y = s.y + step * dir_[k][i][1];
if(can_move(s.x,s.y,_x,_y)){
State temp = s;
temp.x = _x; temp.y = _y;
temp.step = step + 1;
if(k == 0){ /*这一步它向东走*/
if(i == 0){
temp.rote.push_back(2);
temp.now_dir = 2;
}
else
if(i == 1) { /*这一步它向西走*/
temp.rote.push_back(3);
temp.now_dir = 3;
}
}
else if(k == 1){
if(i == 0){ /*这一步它向南走*/
temp.rote.push_back(0);
temp.now_dir = 0;
}
else
if(i == 1){ /*这一步它向北走*/
temp.rote.push_back(1);
temp.now_dir = 1;
}
}
if(step == n &&(_x != LEN ||_y != LEN)) continue;
else
q.push(temp);
}
}
}
printf("Found %d golygon(s).\n",cnt);
}
int main(){
int T;
scanf("%d",&T);
while(T--){
int m;
scanf("%d%d",&n,&m);
memset(Map,0,sizeof(Map));
for(int i = 0 ; i < m ; i++){
int x , y;
scanf("%d%d",&x,&y);
Map[LEN + x][LEN + y] = 1;
}
bfs();
printf("\n");
}
return 0;
}
这个是AC的DFS代码，可以看出来，不同情况下使用DFS和BFS的计算时间差的很大~
| 13970729 | 225 | Golygons | Accepted | C++ | 2.239 | 2014-07-31 10:49:47 |
#include <vector>
#include <list>
#include <map>
#include <string>
#include <set>
#include <cstring>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <ctime>
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
#define MAXD 1000
#define LEN 500
int n,cnt;
int Map[MAXD][MAXD];
int dir[4][2] = {{1,0},{-1,0},{0,1},{0,-1}}; /*向右走，向左走，向上走，向下走*/
int dir_[2][2][2] = {{{0,1},{0,-1}},{{1,0},{-1,0}}};
char const _dir[] = "ewns";
int _vis[50] = {0};
/*0 1 2 3 分别代表向上，向下，向右，向左*/
int rote[MAXD]; /*路线*/
int vis[MAXD][MAXD];
struct Dir{
char str[MAXD];
friend bool operator < (Dir p,Dir q){
if(strcmp(p.str,q.str) < 0)
return true;
else
return false;
}
}ans[200L];
void biao(){
_vis[1] = 1; _vis[2] = 1; _vis[3] = 1; _vis[4] = 1;
_vis[5] = 1; _vis[6] = 1; _vis[9] = 1; _vis[10] = 1;
_vis[11] = 1; _vis[12] = 1; _vis[13] = 1; _vis[14] = 1;
_vis[17] = 1; _vis[18] = 1; _vis[19] = 1; _vis[20] = 1;
}
bool can_move(int from_x,int from_y,int to_x,int to_y){
/*判断能否从(from_x,from_y) 走到 (to_x,to_y) */
if(from_x == to_x){
int t1 = min(from_y,to_y);
int t2 = max(from_y,to_y);
for(int i = t1 ; i <= t2 ; i++){
if(Map[to_x][i])
return false;
}
}
else if(from_y == to_y){
int t1 = min(from_x,to_x);
int t2 = max(from_x,to_x);
for(int i = t1 ; i <= t2 ; i++){
if(Map[i][to_y])
return false;
}
}
return true;
}
void dfs(int step,int dir,int x,int y){ /*当前步数，当前方向，当前位置*/
vis[x][y] = 1;
if(step == n && x == LEN && y == LEN){
for(int i = 0 ; i < step ; i++)
ans[cnt].str[i] = _dir[rote[i]];
ans[cnt].str[step] = '\0';
cnt ++;
return ;
}
else if(step == n)
return ;
int k;
if(dir == 0 || dir == 1)
k = 0;
else
k = 1;
for(int i = 0; i < 2 ; i++){ /*每次只能转90度的弯*/
int _x = x + (step + 1) * dir_[k][i][0];
int _y = y + (step + 1) * dir_[k][i][1];
if(!vis[_x][_y] && can_move(x,y,_x,_y)){
if(k == 0){ /*这一步它向东走*/
if(i == 0){
rote[step] = 2;
dfs(step + 1,2,_x,_y);
}
else
if(i == 1) { /*这一步它向西走*/
rote[step] = 3;
dfs(step + 1,3,_x,_y);
}
}
else if(k == 1){
if(i == 0){ /*这一步它向南走*/
rote[step] = 0;
dfs(step + 1,0,_x,_y);
}
else
if(i == 1){ /*这一步它向北走*/
rote[step] = 1;
dfs(step + 1,1,_x,_y);
}
}
vis[_x][_y] = 0;
}
}
return ;
}
int main(){
int T;
scanf("%d",&T);
biao();
while(T--){
int m;
cnt = 0;
scanf("%d%d",&n,&m);
memset(Map,0,sizeof(Map));
for(int i = 0 ; i < m ; i++){
int x , y;
scanf("%d%d",&x,&y);
Map[LEN + x][LEN + y] = 1;
}
if(!_vis[n]){
for(int i = 0 ; i < 4 ; i++){
int x = LEN + 1 * dir[i][0];
int y = LEN + 1 * dir[i][1];
memset(vis,0,sizeof(vis));
rote[0] = i;
dfs(1,i,x,y);
}
sort(ans,ans + cnt);
for(int i = 0 ; i < cnt ; i++)
printf("%s\n",ans[i].str);
}
printf("Found %d golygon(s).\n",cnt);
printf("\n");
}
return 0;
}