【HDOJ】4932 Miaomiao's Geometry

递归检测。因为dis数组开的不够大，各种wa。写了个数据发生器，果断发现错误，改完就过了。

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <iostream>
 4 #include <algorithm>
 5
 6 using namespace std;
 7
 8 #define MAXN 55
 9
10 int n;
11 double a[MAXN], dis[MAXN*2];
12 char visit[MAXN]; // 0: false, 1: left, 2:right
13
14 bool dfs(int x, double l) {
15     if (x == n-1)
16         return true;
17     if (x == 0) {
18         visit[x] = 2;
19         return dfs(x+1, l);
20     }
21     if (visit[x-1] == 2) {
22         if (a[x-1]+l <= a[x]) {
23             visit[x] = 2;
24             if ( dfs(x+1, l) )
25                 return true;
26         } else if (a[x]+l <= a[x+1]) {
27             visit[x] = 1;
28             return dfs(x+1, l);
29         }
30         return false;
31     } else {
32         if (a[x-1]+2*l <= a[x] || a[x-1]+l==a[x]) {
33             visit[x] = 2;
34             if ( dfs(x+1, l) )
35                 return true;
36         } else if (a[x]+l <= a[x+1]) {
37             visit[x] = 1;
38             return dfs(x+1, l);
39         }
40         return false;
41     }
42 }
43
44 int main() {
45     //FILE *fout = fopen("data", "w");
46     int case_n, m;
47     int i;
48
49     scanf("%d", &case_n);
50     while (case_n--) {
51         scanf("%d", &n);
52         for (i=0; i<n; ++i)
53             scanf("%lf", &a[i]);
54         sort(a, a+n);
55         for (m=0, i=1; i<n; ++i) {
56             dis[m++] = a[i] - a[i-1];
57             dis[m++] = (a[i] - a[i-1])/2;
58         }
59         sort(dis, dis+m);
60         dis[m] = 0.0f;
61         for (i=m-1; i>=0; --i) {
62             if (dis[i] != dis[i+1]) {
63                 memset(visit, 0, sizeof(visit));
64                 if ( dfs(0, dis[i]) )
65                     break;
66             }
67         }
68         printf("%.3lf\n", dis[i]);
69         //fprintf(fout, "%.3lf\n", dis[i]);
70     }
71
72     return 0;
73 }

【HDOJ】4932 Miaomiao's Geometry