【HDOJ】2242 考研路茫茫——空调教室

tarjan缩点，然后树形dp一下可解。重点是重边的处理。

 /* 2242 */
 #include <iostream>
 #include <sstream>
 #include <string>
 #include <map>
 #include <queue>
 #include <set>
 #include <stack>
 #include <vector>
 #include <deque>
 #include <bitset>
 #include <algorithm>
 #include <cstdio>
 #include <cmath>
 #include <ctime>
 #include <cstring>
 #include <climits>
 #include <cctype>
 #include <cassert>
 #include <functional>
 #include <iterator>
 #include <iomanip>
 using namespace std;
 //#pragma comment(linker,"/STACK:102400000,1024000")

 #define sti                set<int>
 #define stpii            set<pair<int, int> >
 #define mpii            map<int,int>
 #define vi                vector<int>
 #define pii                pair<int,int>
 #define vpii            vector<pair<int,int> >
 #define rep(i, a, n)     for (int i=a;i<n;++i)
 #define per(i, a, n)     for (int i=n-1;i>=a;--i)
 #define clr                clear
 #define pb                 push_back
 #define mp                 make_pair
 #define fir                first
 #define sec                second
 #define all(x)             (x).begin(),(x).end()
 #define SZ(x)             ((int)(x).size())
 #define lson            l, mid, rt<<1
 #define rson            mid+1, r, rt<<1|1

 typedef struct {
     int v, nxt;
 } edge_t;

 const int maxv = ;
 const int maxe = ;
 int head[maxv], l;
 edge_t E[maxe];
 int low[maxv], pre[maxv], bn[maxv];
 int S[maxv], top;
 int block, dfs_clock;
 int num[maxv], tot[maxv], sum;
 int head_[maxv], l_;
 edge_t E_[maxe];
 bool visit[maxv];
 int n, m;
 int ans;

 void init() {
     l = block = dfs_clock = ;
     top = ;
     memset(pre, , sizeof(pre));
     memset(bn, , sizeof(bn));
     memset(head, -, sizeof(head));
 }

 void init_() {
     l_ = sum = ;
     memset(tot, , sizeof(tot));
     memset(head_, -, sizeof(head_));
     memset(visit, false, sizeof(visit));
     ans = INT_MAX;
 }

 void addEdge(int u, int v) {
     E[l].v = v;
     E[l].nxt = head[u];
     head[u] = l++;

     E[l].v = u;
     E[l].nxt = head[v];
     head[v] = l++;
 }

 void addEdge_(int u, int v) {
     E_[l_].v = v;
     E_[l_].nxt = head_[u];
     head_[u] = l_++;

     E_[l_].v = u;
     E_[l_].nxt = head_[v];
     head_[v] = l_++;
 }

 void tarjan(int u, int fa) {
     int v, k;
     bool flag = true;

     S[top++] = u;
     pre[u] = low[u] = ++dfs_clock;
     for (k=head[u]; k!=-; k=E[k].nxt) {
         v = E[k].v;
         if (v == fa && flag) {
             flag = false;
             continue;
         }

         if (!pre[v]) {
             tarjan(v, u);
             low[u] = min(low[u], low[v]);
         } else if (!bn[v]) {
             low[u] = min(low[u], pre[v]);
         }
     }

     if (low[u] == pre[u]) {
         ++block;
         do {
             bn[S[--top]] = block;
         } while (S[top]!=u);
     }
 }

 void dfs(int u, int fa) {
     int v, k;

     visit[u] = true;
     for (k=head_[u]; k!=-; k=E_[k].nxt) {
         v = E_[k].v;
         if (v==fa || visit[v])
             continue;
         dfs(v, u);
         tot[u] += tot[v];
     }

     ans = min(ans, abs(sum-tot[u]-tot[u]));
 }

 void solve() {
     rep(i, , n) {
         if (!pre[i])
             tarjan(i, -);
     }

     #ifndef ONLINE_JUDGE
         printf("block = %d\n", block);
     #endif

     if (block <= ) {
         puts("impossible");
         return ;
     }

     init_();
     int u, v, k;

     for (u=; u<n; ++u) {
         tot[bn[u]] += num[u];
         sum += num[u];
         for (k=head[u]; k!=-; k=E[k].nxt) {
             v = E[k].v;
             if (bn[v] != bn[u]) {
                 addEdge_(bn[u], bn[v]);
             }
         }
     }

     dfs(, -);
     printf("%d\n", ans);
 }

 int main() {
     ios::sync_with_stdio(false);
     #ifndef ONLINE_JUDGE
         freopen("data.in", "r", stdin);
         freopen("data.out", "w", stdout);
     #endif

     int u, v;

     while (scanf("%d %d", &n, &m)!=EOF) {
         rep(i, , n)
             scanf("%d", &num[i]);
         init();
         rep(i, , m) {
             scanf("%d %d", &u, &v);
             addEdge(u, v);
         }
         solve();
     }

     #ifndef ONLINE_JUDGE
         printf("time = %d.\n", (int)clock());
     #endif

     return ;
 }

数据生成器。

 import sys
 import string
 from random import randint

 def GenData(fileName):
     with open(fileName, "w") as fout:
         t = 10
         for tt in xrange(t):
             n = randint(100, 200)
             m = randint(n/10, n+n/10)
             fout.write("%d %d\n" % (n, m))
             dataList = []
             for i in xrange(n):
                 x = randint(0, 1000)
                 dataList.append(x)
             fout.write(" ".join(map(str, dataList)) + "\n")
             for i in xrange(m):
                 a = randint(0, n)
                 b = randint(0, n)
                 fout.write("%d %d\n" % (a, b))

 def MovData(srcFileName, desFileName):
     with open(srcFileName, "r") as fin:
         lines = fin.readlines()
     with open(desFileName, "w") as fout:
         fout.write("".join(lines))

 def CompData():
     print "comp"
     srcFileName = "F:\Qt_prj\hdoj\data.out"
     desFileName = "F:\workspace\cpp_hdoj\data.out"
     srcLines = []
     desLines = []
     with open(srcFileName, "r") as fin:
         srcLines = fin.readlines()
     with open(desFileName, "r") as fin:
         desLines = fin.readlines()
     n = min(len(srcLines), len(desLines))-1
     for i in xrange(n):
         ans2 = int(desLines[i])
         ans1 = int(srcLines[i])
         if ans1 > ans2:
             print "%d: wrong" % i

 if __name__ == "__main__":
     srcFileName = "F:\Qt_prj\hdoj\data.in"
     desFileName = "F:\workspace\cpp_hdoj\data.in"
     GenData(srcFileName)
     MovData(srcFileName, desFileName)