【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 }
