HDU 4770 lights against dudely (violent)

HDU 4770 lights against dudely

Question Link

Given a lamp, there is a lamp that can be rotated. Ask at least a few lights that can be illuminated and cannot be illuminated #

Idea: brute-force solution: Enumerate special lights first, and then enumerate normal lights. pruning is required. Otherwise, it will

Code:

#include <stdio.h>#include <string.h>#include <algorithm>using namespace std;const int INF = 0x3f3f3f3f;const int N = 205;const int d[4][3][2] = {{{0, 0}, {-1, 0}, {0, 1}},{{0, 0}, {1, 0}, {0, 1}},{{0, 0}, {1, 0}, {0, -1}},{{0, 0}, {-1, 0}, {0, -1}}};int n, m, g[N][N], x[N], y[N], pn, light[N][N], put[N][N], ans;char str[N];bool judge(int x, int y, const int d[][2], int &ans) {    if (put[x][y]) return false;    ans = 0;    for (int i = 0; i < 3; i++) {int xx = x + d[i][0];int yy = y + d[i][1];if (xx > n || xx < 1 || yy > m || yy < 1) continue;if (!g[xx][yy]) return false;    }    for (int i = 0; i < 3; i++) {int xx = x + d[i][0];int yy = y + d[i][1];if (xx > n || xx < 1 || yy > m || yy < 1) continue;if (light[xx][yy] == 0) ans++;light[xx][yy]++;    }    return true;}bool judge2(int now) {    for (int i = 0; i < pn; i++) {if (x[i] <= now) break;if (!light[x[i]][y[i]]) return false;    }    return true;}int dfs(int now, int li, int num) {    if (num > ans) return INF;    if (!judge2(x[now])) return INF;    if (li == 0) return num;    if (now == pn) return INF;    int tmp;    int ans = INF;    if (judge(x[now], y[now], d[0], tmp)) {ans = min(ans, dfs(now + 1, li - tmp, num + 1));for (int i = 0; i < 3; i++) {    int xx = x[now] + d[0][i][0];    int yy = y[now] + d[0][i][1];    if (xx > n || xx < 1 || yy > m || yy < 1) continue;    light[xx][yy]--;}    }    ans = min(ans, dfs(now + 1, li, num));    return ans;}int main() {    while (~scanf("%d%d", &n, &m) && n || m) {for (int i = 1; i <= n; i++) {    scanf("%s", str + 1);    for (int j = 1; j <= m; j++)g[i][j] = (str[j] == '.'?1:0);}pn = 0;for (int i = n; i >= 1; i--) {    for (int j = 1; j <= m; j++) {if (g[i][j]) {    x[pn] = i;    y[pn] = j;    pn++;}    }}memset(light, 0, sizeof(light));ans = INF;ans = dfs(0, pn, 0);for (int i = 0; i < pn; i++) {    for (int j = 0; j < 4; j++) {int tmp = 0;memset(light, 0, sizeof(light));if (judge(x[i], y[i], d[j], tmp)) {    put[x[i]][y[i]] = 1;    ans = min(ans, dfs(0, pn - tmp, 1));    put[x[i]][y[i]] = 0;}    }}if (ans == INF) printf("-1\n");else printf("%d\n", ans);    }    return 0;}