BZOJ2208

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define Maxlen (50005 << 2) * 300
 4 char buf[Maxlen], *c = buf;
 5 int Len;
 6 
 7 void init() {
 8     Len = fread(c, 1, Maxlen, stdin);
 9     buf[Len] = ‘\0‘;
10 }
11 
12 template <typename T>
13 inline T read() {
14     register T x = 0, f = 1;
15     while (!isdigit(*c)) {
16         if (*c == ‘-‘)f = -1; ++c;
17     }
18     while (isdigit(*c)) {
19         x = x * 10 + *c - ‘0‘; ++c;
20     }
21     return x * f;
22 }
23 
24 template <typename T>
25 inline T sread() {
26     register T x = 0, f = 1;
27     while (!isdigit(*c)) {
28         if (*c == ‘-‘)f = -1; ++c;
29     }
30     x = *c - ‘0‘; ++c;
31     return x * f;
32 }
33 
34 #define read() read<int>()
35 #define sread() sread<int>()
36 /*------------------------------template------------------------------*/
37 
38 int visited[2020];
39 int n, cnt = 0;
40 vector<int> edge[2020];
41 int dfs(int k) {
42     int ret = 0;
43     for (int i = 0; i < edge[k].size(); i ++) 
44         if (!visited[edge[k][i]]){
45             visited[edge[k][i]] = 1;
46             ret += dfs(edge[k][i]) + 1;
47     }
48     return ret;
49 }
50 
51 int main() {
52     init();
53     n = read();
54     for (int i = 1; i <= n; i ++) {
55         for (int j = 1; j <= n;j ++) {
56             int x = sread();
57             if (x) {
58                 edge[i].push_back(j);
59             }
60         }
61     } int ans = 0;
62     for (int i = 1; i <= n; i ++) {
63         memset(visited, 0, sizeof(visited));
64         visited[i] = 1;
65         ans += dfs(i) + 1;
66     }
67     printf("%d\n", ans);
68 }