hihoCoder 1233 Boxes（bfs）

题目链接：hihoCoder 1233 Boxes

解题思路

确定n，bfs预处理出所有可达状态。

代码

#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>
#include <algorithm>

using namespace std;
const int maxn = 10;
const int maxs = 1e6;
const int dir[2] = {1, -1};
const int inf = 0x3f3f3f3f;
typedef pair<int,int> pii;

int N, E, V[maxn], P[maxn], T[maxn], vis[8][maxs];

int idx(int* c) {
    int ret = 0;
    for (int i = 0; i < N; i++)
        ret = ret * N + c[i];
    return ret;
}

void ridx(int* c, int s) {
    for (int i = N-1; i >= 0; i--) {
        c[i] = s % N;
        s /= N;
    }
}

bool judge (int w, int u, int p) {
    if (p < 0 || p >= N) return false;
    return w < T[p] && w == T[u];
}

void bfs (int n, int* v) {
    N = n;
    for (int i = 0; i < N; i++) V[i] = T[i] = i;
    int s = idx(T);
    v[s] = 0;

    queue<pii> Q;
    Q.push(make_pair(s, 0));

    while (!Q.empty()) {
        int u = Q.front().first;
        int c = Q.front().second;
        Q.pop();

        ridx(P, u);
        for (int i = 0; i < N; i++) T[i] = inf;
        for (int i = 0; i < N; i++) T[P[i]] = min(T[P[i]], V[i]);

        for (int i = 0; i < N; i++) {
            for (int j = 0; j < 2; j++) {
                if (judge(V[i], P[i], P[i]+dir[j])) {
                    P[i] += dir[j];
                    int e = idx(P);
                    if (v[e] == -1) {
                        Q.push(make_pair(e, c+1));
                        v[e] = c+1;
                    }
                    P[i] -= dir[j];
                }
            }
        }
    }
}

void init () {
    scanf("%d", &N);
    for (int i = 0; i < N; i++) scanf("%d", &V[i]);
    memcpy(P, V, sizeof(V));

    sort(P, P + N);
    for (int i = 0; i < N; i++) T[i] = lower_bound(P, P + N, V[i]) - P;
    for (int i = 0; i < N; i++) P[T[i]] = i;
    //for (int i = 0; i < N; i++) printf("%d ", P[i]);
    //printf("\n");
    E = idx(P);
}

int main () {
    int cas;
    scanf("%d", &cas);
    memset(vis, -1, sizeof(vis));
    for (int i = 1; i < 8; i++) bfs(i, vis[i]);
    while (cas--) {
        init();
        printf("%d\n", vis[N][E]);
    }
    return 0;
}