没事做水了一道POJ的简单BFS的题目
这道题的数据范围是20,所以状态总数就是（1<<20）
第一次提交使用STL的queue，并且是在队首判断是否达到终点，达到终点就退出，超时：（其实这里我是很不明白的，，TM状态总数就只有1e6怎么也不应该超时的，，，，只能说STL的queue的常数实在是太大，完全没法弄。。。）
1 #include <map>
2 #include <set>
3 #include <stack>
4 #include <queue>
5 #include <cmath>
6 #include <ctime>
7 #include <vector>
8 #include <cstdio>
9 #include <cctype>
10 #include <cstring>
11 #include <string.h>
12 #include <cstdlib>
13 #include <iostream>
14 #include <algorithm>
15 using namespace std;
16 #define INF 1e9
17 #define inf (-((LL)1<<40))
18 #define lson k<<1, L, mid
19 #define rson k<<1|1, mid+1, R
20 #define mem0(a) memset(a,0,sizeof(a))
21 #define mem1(a) memset(a,-1,sizeof(a))
22 #define mem(a, b) memset(a, b, sizeof(a))
23 #define FOPENIN(IN) freopen(IN, "r", stdin)
24 #define FOPENOUT(OUT) freopen(OUT, "w", stdout)
25 template<class T> T CMP_MIN(T a, T b) { return a < b; }
26 template<class T> T CMP_MAX(T a, T b) { return a > b; }
27 template<class T> T MAX(T a, T b) { return a > b ? a : b; }
28 template<class T> T MIN(T a, T b) { return a < b ? a : b; }
29 template<class T> T GCD(T a, T b) { return b ? GCD(b, a%b) : a; }
30 template<class T> T LCM(T a, T b) { return a / GCD(a,b) * b; }
31 template<class T> void SWAP(T& a, T& b) { T x = a; a = b; b = x; }
32
33 //typedef __int64 LL;
34 typedef long long LL;
35 const int MAXN = 200010;
36 const int MAXM = 100005;
37 const double eps = 1e-10;
38 //const LL MOD = 1000000007;
39
40 int step[1<<21];
41 bool vis[1<<21];
42
43 int BFS(int s)
44 {
45 vis[s] = 1;
46 queue<int>q;
47 q.push(s);
48 step[s] = 0;
49 while(!q.empty())
50 {
51 int u = q.front(); q.pop();
52 if(u == 0) return step[u];
53 for(int i=1;i<19;i++)
54 {
55 int r = u;
56 r ^= (1<<i-1) | (1<<i) | (1<<i+1);
57 if(!vis[r])
58 {
59 vis[r] = 1;
60 step[r] = step[u] + 1;
61 q.push(r);
62 }
63 }
64 int r = u ^ (1<<0) ^ (1<<1);
65 if(!vis[r]) { vis[r] = 1; step[r] = step[u] + 1; q.push(r); }
66 r = u ^ (1<<18) ^ (1<<19);
67 if(!vis[r]) { vis[r] = 1; step[r] = step[u] + 1; q.push(r); }
68 }
69 return -1;
70 }
71
72 int main()
73 {
74 //FOPENIN("in.txt");
75 int st = 0, x;
76 for(int i=0;i<20;i++)
77 {
78 scanf("%d", &x);
79 st |= (x<<i);
80 }
81 printf("%d\n", BFS(st));
82 return 0;
83 }
TLE后马上把判断放到队尾（就是说在一个状态进队列前先判断是不是终点状态，是的话就退出），跑了875ms，勉强过了，，（这里我就是乱改的了，代码没任何观赏性）
1 #include <map>
2 #include <set>
3 #include <stack>
4 #include <queue>
5 #include <cmath>
6 #include <ctime>
7 #include <vector>
8 #include <cstdio>
9 #include <cctype>
10 #include <cstring>
11 #include <string.h>
12 #include <cstdlib>
13 #include <iostream>
14 #include <algorithm>
15 using namespace std;
16 #define INF 1e9
17 #define inf (-((LL)1<<40))
18 #define lson k<<1, L, mid
19 #define rson k<<1|1, mid+1, R
20 #define mem0(a) memset(a,0,sizeof(a))
21 #define mem1(a) memset(a,-1,sizeof(a))
22 #define mem(a, b) memset(a, b, sizeof(a))
23 #define FOPENIN(IN) freopen(IN, "r", stdin)
24 #define FOPENOUT(OUT) freopen(OUT, "w", stdout)
25 template<class T> T CMP_MIN(T a, T b) { return a < b; }
26 template<class T> T CMP_MAX(T a, T b) { return a > b; }
27 template<class T> T MAX(T a, T b) { return a > b ? a : b; }
28 template<class T> T MIN(T a, T b) { return a < b ? a : b; }
29 template<class T> T GCD(T a, T b) { return b ? GCD(b, a%b) : a; }
30 template<class T> T LCM(T a, T b) { return a / GCD(a,b) * b; }
31 template<class T> void SWAP(T& a, T& b) { T x = a; a = b; b = x; }
32
33 //typedef __int64 LL;
34 typedef long long LL;
35 const int MAXN = 200010;
36 const int MAXM = 100005;
37 const double eps = 1e-10;
38 //const LL MOD = 1000000007;
39
40 int step[1<<21];
41 bool vis[1<<21];
42
43 int BFS(int s)
44 {
45 vis[s] = 1;
46 queue<int>q;
47 q.push(s);
48 step[s] = 0;
49 while(!q.empty())
50 {
51 int u = q.front(); q.pop();
52 if(u == 0) return step[u];
53 for(int i=1;i<19;i++)
54 {
55 int r = u;
56 r ^= (1<<i-1) | (1<<i) | (1<<i+1);
57 if(!vis[r])
58 {
59 vis[r] = 1;
60 step[r] = step[u] + 1;
61 if(r==0) return step[r];
62 q.push(r);
63 }
64 }
65 int r = u ^ (1<<0) ^ (1<<1);
66 if(!vis[r]) { vis[r] = 1; step[r] = step[u] + 1; q.push(r); if(r==0) return step[r];}
67 r = u ^ (1<<18) ^ (1<<19);
68 if(!vis[r]) { vis[r] = 1; step[r] = step[u] + 1; q.push(r); if(r==0) return step[r];}
69 }
70 return -1;
71 }
72
73 int main()
74 {
75 //FOPENIN("in.txt");
76 int st = 0, x;
77 for(int i=0;i<20;i++)
78 {
79 scanf("%d", &x);
80 st |= (x<<i);
81 }
82 printf("%d\n", BFS(st));
83 return 0;
84 }
然后突然想起之前写过一个静态队列的模板，是用循环队列写的，想着正好去测试下，就改了队列的定义，其他使用完全一致，没任何修改，结果跑了250ms快了好多了啊有木有。。
1 #include <map>
2 #include <set>
3 #include <stack>
4 #include <queue>
5 #include <cmath>
6 #include <ctime>
7 #include <vector>
8 #include <cstdio>
9 #include <cctype>
10 #include <cstring>
11 #include <string.h>
12 #include <cstdlib>
13 #include <iostream>
14 #include <algorithm>
15 using namespace std;
16 #define INF 1e9
17 #define inf (-((LL)1<<40))
18 #define lson k<<1, L, mid
19 #define rson k<<1|1, mid+1, R
20 #define mem0(a) memset(a,0,sizeof(a))
21 #define mem1(a) memset(a,-1,sizeof(a))
22 #define mem(a, b) memset(a, b, sizeof(a))
23 #define FOPENIN(IN) freopen(IN, "r", stdin)
24 #define FOPENOUT(OUT) freopen(OUT, "w", stdout)
25 template<class T> T CMP_MIN(T a, T b) { return a < b; }
26 template<class T> T CMP_MAX(T a, T b) { return a > b; }
27 template<class T> T MAX(T a, T b) { return a > b ? a : b; }
28 template<class T> T MIN(T a, T b) { return a < b ? a : b; }
29 template<class T> T GCD(T a, T b) { return b ? GCD(b, a%b) : a; }
30 template<class T> T LCM(T a, T b) { return a / GCD(a,b) * b; }
31 template<class T> void SWAP(T& a, T& b) { T x = a; a = b; b = x; }
32
33 //typedef __int64 LL;
34 typedef long long LL;
35 const int MAXN = 200010;
36 const int MAXM = 100005;
37 const double eps = 1e-10;
38 //const LL MOD = 1000000007;
39
40
41 //MyQueue<Type>q;
42 //定义了一个固定长度的队列， 不能动态增长
43 //构造时不传参数，队列大小为1e5，传入参数时为自定义大小
44 //如果队列不为空，front返回队首元素，
45 //如果队列为空，pop无效，front返回NULL
46 //clear将队列清空, 供多次使用
47 //如果push时产生冲突，即队列已满， 将加入失败
48 template <class T>
49 class MyQueue
50 {
51 private:
52 T* que;
53 int si, fr, re;
54 void setValue(int _size) {
55 fr = 0; re = 0;
56 si = _size;
57 que = (T*)malloc(si * sizeof(T));
58 }
59 public:
60 MyQueue() {
61 this->setValue(100005);
62 }
63 MyQueue(int _size) {
64 this->setValue(_size);
65 }
66 T front() {
67 if(fr != re)
68 return que[fr];
69 return NULL;
70 }
71 void pop() {
72 if(fr != re)
73 fr = (fr + 1) % si;
74 }
75 void push(T e) {
76 if((re + 1) % si == fr) return ;
77 que[re] = e;
78 re = (re + 1) % si;
79 }
80 bool empty() {
81 if(fr == re) return 1;
82 return 0;
83 }
84 void clear() {
85 fr = 0;
86 re = 0;
87 }
88 };
89
90 int step[1<<21];
91 bool vis[1<<21];
92
93 int BFS(int s)
94 {
95 vis[s] = 1;
96 MyQueue<int>q(1<<21);//定义队列的大小为(1<<21),其他无任何修改
97 q.push(s);
98 step[s] = 0;
99 while(!q.empty())
100 {
101 int u = q.front(); q.pop();
102 if(u == 0) return step[u];
103 for(int i=1;i<19;i++)
104 {
105 int r = u;
106 r ^= (1<<i-1) | (1<<i) | (1<<i+1);
107 if(!vis[r])
108 {
109 vis[r] = 1;
110 step[r] = step[u] + 1;
111 q.push(r);
112 }
113 }
114 int r = u ^ (1<<0) ^ (1<<1);
115 if(!vis[r]) { vis[r] = 1; step[r] = step[u] + 1; q.push(r); }
116 r = u ^ (1<<18) ^ (1<<19);
117 if(!vis[r]) { vis[r] = 1; step[r] = step[u] + 1; q.push(r); }
118 }
119 return -1;
120 }
121
122 int main()
123 {
124 //FOPENIN("in.txt");
125 int st = 0, x;
126 for(int i=0;i<20;i++)
127 {
128 scanf("%d", &x);
129 st |= (x<<i);
130 }
131 printf("%d\n", BFS(st));
132 return 0;
133 }
最后试着把终点判断放在队头，依然360ms就跑出来了啊，，，我就哭了。。。
POJ3185(简单BFS，主要做测试使用)
时间： 2024-08-07 09:39:42