2009年 12月 09日星期三.sgu134 sgu133 sgu181

简单的树形动态规划
贴代码

1 /*
2 * SOUR:sgu 134
3 * ALGO:tree dp
4 * DATE: 2009年 12月 09日星期三 16:28:16 CST
5 * COMM:3
6 * */
7 #include < iostream >
8 #include < cstdio >
9 #include < cstdlib >
10 #include < cstring >
11 #include < algorithm >
12 #include < vector >
13 using namespace std;
14 typedef long long LL;
15 const int maxint = 0x7fffffff ;
16 const long long max64 = 0x7fffffffffffffffll;
17 const int N = 16100 ;
18 #define pb(x) push_back(x)
19 vector < int > g[N];
20 int vis[N];
21 int n,res = maxint, out [N],top;
22 void ckmax( int & a, int b) { if (a < b) a = b;}
23 int dfs( int u)
24 {
25      // printf("dfs = %d\n",u);
26     vis[u] = true ;
27      int sum = 0 ,val = 0 ,tmp;
28      for ( int i = 0 ;i < g[u].size();i ++ ) {
29          int v = g[u][i];
30          if ( ! vis[v]) {
31             tmp = dfs(v);
32             sum += tmp;
33             ckmax(val,tmp);
34         }
35     }
36     tmp = n - 1 - sum;
37     ckmax(val,tmp);
38      if (res > val) {
39         res = val,top = 1 , out [ 0 ] = u;
40     } else if (val == res) {
41          out [top ++ ] = u;
42     }
43      return sum + 1 ;
44 }
45
46 int main()
47 {
48      int i,j,k,a =- 1 ,b;
49     scanf( " %d " , & n);
50      for (i = 1 ;i < n;i ++ ) {
51         scanf( " %d%d " , & a, & b);
52         g[a].pb(b);
53         g[b].pb(a);
54     }
55      if (a != - 1 ) {
56         dfs(a);
57         printf( " %d %d\n " ,res,top);
58         sort( out , out + top);
59          if (top > 0 ) printf( " %d " , out [ 0 ]);
60          for (i = 1 ;i < top;i ++ ) {
61             printf( " %d " , out [i]);
62         }
63         putchar( 10 );
64     } else {
65         printf( " 0 0\n " );
66     }
67      return 0 ;
68 }
69
70

sgu133 排序，看你几分钟能想出来

1     scanf( " %d " , & n);
2      for (i = 0 ;i < n;i ++ ) {
3         scanf( " %d%d " , & a[i].l, & a[i].r);
4     }
5     sort(a,a + n,cmp);
6      int res = 0 ,pre = - 1 ;
7      for (i = 0 ;i < n;i ++ ) {
8          if (a[i].r < pre) {
9             res ++ ;
10         }
11         pre = max(pre,a[i].r);
12     }
13     printf( " %d\n " ,res);
14

sgu181 算一个递推式的第k项，很容易错

1 /*
2 * SOUR:sgu181
3 * ALGO:math
4 * DATE: 2009年 12月 11日星期五 21:50:18 CST
5 * COMM:3
6 * 注意k可能出现在循环节开始之前
7 * */
8 #include < iostream >
9 #include < cstdio >
10 #include < cstdlib >
11 #include < cstring >
12 #include < algorithm >
13 using namespace std;
14 typedef long long LL;
15 const int maxint = 0x7fffffff ;
16 const long long max64 = 0x7fffffffffffffffll;
17
18 LL A,alpha,beta,gamma,M,k;
19 const int N = 20010 ;
20 LL vis[N];
21 LL val[N];
22 int main()
23 {
24     LL i;
25      /*
26        1)    x0 = A;
27        2)    xi = (alpha * x(i-1)^2 + beta * x(i-1) + gamma) mod M, for i >= 1.
28      * */
29      // A (1 <= A <= 10000), alpha (0 <= alpha <= 100), beta (0 <= beta <= 100), gamma
30      // (0 <= gamma <= 100), M (1 <= M <= 1000), k (0 <= k <= 10^9)
31
32     fill(vis,vis + N, - 1 );
33     cin >> A >> alpha >> beta >> gamma >> M >> k;
34     LL xi = A,step = 0 ,cycle,before;
35      while ( 1 ) {
36          if (vis[xi] >= 0 ) {
37             cycle = step - vis[xi];
38             before = vis[xi];
39              break ;
40         }
41         val[step] = xi;
42         vis[xi] = step ++ ;
43
44            xi = (alpha * xi * xi + beta * xi + gamma) % M;
45     }
46      if (k < step ) {
47         cout << val[k] << endl;
48     } else {
49         LL idx = (k - before) % cycle + before;
50         cout << val[idx] << endl;
51     }
52
53      return 0 ;
54 }
55
56

2009年 12月 09日 星期三.sgu134 sgu133 sgu181