ZOJ 3865 Superbot BFS 搜尋

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 不知道為什麼比賽的時候一直想著用DFS 來寫

一直想剪枝結果還是TLE = = 

這題資料量不大，又是問最優解，那麼一般來說是用 BFS 來寫

 

int commandi[4] = {1, 2, 3, 4};

我定義了一個方向數組，其實題目意思中的，指標移動還有操作版的變化本質上都是指標的移動

在此只需要 額外定義一個變數 cur 在數組 commandi 中迴圈移動即可

 

這道題目還是因為資料量不大吧，直接用 STL 中的 Queue 即可，優先隊列肯定會更快。

總體來說，還是一道容易題。

 

Source Code :

//#pragma comment(linker, "/STACK:16777216") //for c++ Compiler#include <stdio.h>#include <iostream>#include <fstream>#include <cstring>#include <cmath>#include <stack>#include <string>#include <map>#include <set>#include <queue>#include <list>#include <vector>#include <algorithm>#define Max(a,b) (((a) > (b)) ? (a) : (b))#define Min(a,b) (((a) < (b)) ? (a) : (b))#define Abs(x) (((x) > 0) ? (x) : (-(x)))#define MOD 1000000007#define pi acos(-1.0)using namespace std;typedef long long           ll      ;typedef unsigned long long  ull     ;typedef unsigned int        uint    ;typedef unsigned char       uchar   ;template<class T> inline void checkmin(T &a,T b){if(a>b) a=b;}template<class T> inline void checkmax(T &a,T b){if(a<b) a=b;}const double eps = 1e-7      ;const int N = 210            ;const int M = 1100011*2      ;const ll P = 10000000097ll   ;const int MAXN = 10900000    ;const int INF = 0x3f3f3f3f   ;const int dir_x[5] = {0, 0, 0, -1, 1};const int dir_y[5] = {0, -1, 1, 0, 0};struct sc {    int x, y;    int time;    int cur;} st, ed;int n, m, p;char a[20][20];bool vis[20][20][5];int commandi[4] = {1, 2, 3, 4};queue <sc> q;bool check (int x, int y) {    return x >= 1 && x <= n && y >= 1 && y <= m;}int left (int &cur) {    cur = (cur - 1 + 4) % 4;}int right (int & cur) {    cur = (cur + 1 + 4) % 4;}void solve (struct sc v) {    ++v.time;    if (v.time % p == 0) {        left (v.cur);    }    if (vis[v.x][v.y][commandi [v.cur]] == false) {        vis[v.x][v.y][commandi [v.cur]] = true;        q.push (v);    }}void bfs () {    int ans = -INF;    sc e;    e = st;    e.time = 0;    e.cur = 0;    memset (vis, 0, sizeof (vis));    vis [e.x][e.y][commandi [e.cur]] = true;    q.push (e);    while (!q.empty ()) {        sc u = q.front ();        q.pop ();        if ((u.x == ed.x && u.y == ed.y) || ‘$‘ == a[u.x][u.y]) {            ans = u.time;            break;        }        sc v = u;   //to left        left (v.cur);        solve (v);        v = u;      //to right        right (v.cur);        solve (v);        v = u;      //wait        solve (v);        v = u;      //press        int dr = commandi [v.cur];        v.x += dir_x[dr];        v.y += dir_y[dr];        if (!check (v.x, v.y))  continue;        if (‘*‘ == a[v.x][v.y]) continue;        solve (v);    }    if (-INF == ans) {        cout << "YouBadbad" << endl;    } else {        cout << ans << endl;    }}int main () {    int i, j, t;    cin >> t;    while (t--) {        while (!q.empty ()) q.pop ();        cin >> n >> m >> p;        for (i = 1; i <= n; ++i) {            for (j = 1; j <= m; ++j) {                cin >> a[i][j];                if (‘@‘ == a[i][j]) {                    st.x = i;                    st.y = j;                } else if (‘$‘ == a[i][j]) {                    ed.x = i;                    ed.y = j;                }            }        }        bfs ();    }    return 0;}/*10 10 3@..................................................................................................$10 5 3@................................................$*/

 

ZOJ 3865 Superbot BFS 搜尋