BZOJ3624 [Apio2008]免费道路

就是贪心的想法。。。先取1的再取0的边

验证一下满不满足要求以后，再做一遍生成树。

反正Kruskal是O(m)的无压力2333

 

 1 /**************************************************************
 2     Problem: 3624
 3     User: rausen
 4     Language: C++
 5     Result: Accepted
 6     Time:60 ms
 7     Memory:16416 kb
 8 ****************************************************************/
 9  
10 #include <cstdio>
11  
12 using namespace std;
13 const int N = 20005;
14 const int M = 100005;
15 const int Maxlen = 15000010;
16  
17 struct edges {
18     int x, y;
19     edges() {}
20     edges(int _x, int _y) : x(_x), y(_y) {}
21 }e[M];
22  
23 int n, m, k, cnt;
24 int fa[N];
25 bool vis[M];
26  
27 char buf[Maxlen];
28 int Len, Left;
29  
30 inline int read() {
31     int x = 0;
32     while (buf[Left] < '0' || '9' < buf[Left]) ++Left;
33     while ('0' <= buf[Left] && buf[Left] <= '9')
34         x = x * 10 + buf[Left++] - '0';
35     return x;
36 }
37    
38 int len = 0, pr[15];
39 inline void print(int x) {
40     if (x < 0) putchar('-'), x = -x;
41     while (x)
42         pr[++len] = x % 10, x /= 10;
43     if (!len) putchar('0');
44     while (len)
45         putchar(pr[len--] + '0');
46 }
47  
48  
49 int find_fa(int x) {
50     return fa[x] == x ? x : fa[x] = find_fa(fa[x]);
51 }
52  
53 int main() {
54     int i, x, y, f, L, R, fa1, fa2;
55     Len = fread(buf, 1, Maxlen, stdin);
56     buf[Len] = ' ';
57     n = read(), m = read(), k = read();
58     for (i = 1, L = 0, R = m + 1; i <= m; ++i) {
59         x = read(), y = read(), f = read();
60         if (f) e[++L] = edges(x, y);
61         else e[--R] = edges(x, y);
62     }
63      
64     for (i = 1; i <= n; ++i) fa[i] = i;
65     for (i = 1; i <= m; ++i)
66         if ((fa1 = find_fa(e[i].x)) != (fa2 = find_fa(e[i].y))) {
67             fa[fa1] = fa2;
68             if (i > L)
69                 vis[i] = 1, cnt += 1;
70         }
71     if (cnt > k) {
72         puts("no solution");
73         return 0;
74     }
75      
76     for (i = 1; i <= n; ++i) fa[i] = i;
77     for (i = R; i <= m; ++i)
78         if (vis[i]) fa[find_fa(e[i].x)] = find_fa(e[i].y);
79     for (i = R; i <= m; ++i)
80         if (!vis[i] && cnt < k && (fa1 = find_fa(e[i].x)) != (fa2 = find_fa(e[i].y))) {
81             fa[fa1] = fa2, vis[i] = 1;
82             ++cnt;
83         }
84     if (cnt != k) {
85         puts("no solution");
86         return 0;
87     }
88      
89     for (i = 1; i <= L; ++i)
90         if ((fa1 = find_fa(e[i].x)) != (fa2 = find_fa(e[i].y)))
91             fa[fa1] = fa2, vis[i] = 1;
92     for (i = 1; i <= m; ++i)
93         if (vis[i]) {
94             print(e[i].x), putchar(' ');
95             print(e[i].y), putchar(' ');
96             print(i <= L), putchar('\n');
97         }
98 }
View Code

（p.s. 用IO外挂骗了个Rank.1，液！）

（p.s. 另：试了一下。。。putchar和putc差不多快，但是fputc和fwrite好慢。。。不知为何呢？）

posted on 2014-11-22 10:09  Xs酱~  阅读(445)  评论(0)  编辑  收藏  举报