hihoCoder 1233 Boxes（bfs）

解题思路

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
[E]);
}
return 0;
}