【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 = 10005;
const int maxe = 40005;
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 = 0;
    top = 0;
    memset(pre, 0, sizeof(pre));
    memset(bn, 0, sizeof(bn));
    memset(head, -1, sizeof(head));
}

void init_() {
    l_ = sum = 0;
    memset(tot, 0, sizeof(tot));
    memset(head_, -1, 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!=-1; 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!=-1; 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, 0, n) {
        if (!pre[i])
            tarjan(i, -1);
    }

    #ifndef ONLINE_JUDGE
        printf("block = %d
", block);
    #endif
    
    if (block <= 1) {
        puts("impossible");
        return ;
    }

    init_();
    int u, v, k;

    for (u=0; u<n; ++u) {
        tot[bn[u]] += num[u];
        sum += num[u];
        for (k=head[u]; k!=-1; k=E[k].nxt) {
            v = E[k].v;
            if (bn[v] != bn[u]) {
                addEdge_(bn[u], bn[v]);
            }
        }
    }

    dfs(1, -1);
    printf("%d
", 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, 0, n)
            scanf("%d", &num[i]);
        init();
        rep(i, 0, m) {
            scanf("%d %d", &u, &v);
            addEdge(u, v);
        }
        solve();
    }

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

    return 0;
}

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, m))
            dataList = []
            for i in xrange(n):
                x = randint(0, 1000)
                dataList.append(x)
            fout.write(" ".join(map(str, dataList)) + "
")
            for i in xrange(m):
                a = randint(0, n)
                b = randint(0, n)
                fout.write("%d %d
" % (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_prjhdojdata.out"
    desFileName = "F:workspacecpp_hdojdata.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_prjhdojdata.in"
    desFileName = "F:workspacecpp_hdojdata.in"
    GenData(srcFileName)
    MovData(srcFileName, desFileName)