【HDOJ】2732 Leapin' Lizards

贪心+网络流。对于每个结点，构建入点和出点。
对于每一个lizard>0,构建边s->in position of lizard， 容量为1.
对于pillar>0, 构建边in position of pillar -> out position of pillar, 容量为number of pillar.
若沿四个方向移动距离d可以超过边界，则构建边out position of pillar -> t， 容量为INF；
否则， 对于曼哈顿距离l(l>0 and l<=d)的点p构建边out position of pillar -> in position p, 容量为INF。（此时，不用考虑p是否含有pillar，无所谓）
Dinic可解网络流。一定要注意输出was/were，单复数和0等。

/* 2732 */
#include <iostream>
#include <string>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>
#include <deque>
#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

const int INF = 0x1f1f1f1f;
const int maxn = 25;
const int maxv = maxn*maxn*2;
const int maxe = maxv*maxn*8;
int V[maxe], F[maxe], nxt[maxe];
int head[maxv], dis[maxv];
char Ps[maxn][maxn], Ls[maxn][maxn];
int dir[4][2] = {
    -1, 0, 1, 0, 0, -1, 0, 1
};
int n, m;

void addEdge(int u, int v, int c) {
    V[m] = v;
    F[m] = c;
    nxt[m] = head[u];
    head[u] = m++;
    
    V[m] = u;
    F[m] = 0;
    nxt[m] = head[v];
    head[v] = m++;
}

bool bfs(int s, int t) {
    queue<int> Q;
    int u, v, k;
    
    memset(dis, 0, sizeof(dis));
    Q.push(s);
    dis[s] = 1;
    
    while (!Q.empty()) {
        u = Q.front();
        Q.pop();
        for (k=head[u]; k!=-1; k=nxt[k]) {
            v = V[k];
            if (!dis[v] && F[k]) {
                dis[v] = dis[u] + 1;
                Q.push(v);
            }
        }
    }
    
    return dis[t]==0;
}

int dfs(int u, int t, int val) {
    if (u==t || val==0)
        return val;
    
    int ret = 0;
    int tmp, v, k;
    
    for (k=head[u]; k!=-1; k=nxt[k]) {
        v = V[k];
        if (dis[v]==dis[u]+1 && F[k] && (tmp=dfs(v, t, min(val, F[k])))>0) {
            F[k] -= tmp;
            F[k^1] += tmp;
            ret += tmp;
            val -= tmp;
            if (val == 0)
                break;
        }
    }
    
    return ret;
}

int Dinic(int s, int t) {
    int ret = 0, tmp;
    
    while (1) {
        if (bfs(s, t))
            break;
        
        tmp = dfs(s, t, INF);
        ret += tmp;
    }
    
    return ret;
}

int main() {
    ios::sync_with_stdio(false);
    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif
    
    int case_n;
    int s, t, n_, m_, d, tmp;
    int x, y;
    int k, id, id_;
    int ans, tot;
    bool flag;
    
    scanf("%d", &case_n);
    rep(tt, 1, case_n+1) {
        scanf("%d %d", &n_, &d);
        
        rep(i, 1, n_+1)
            scanf("%s", Ps[i]+1);
        rep(i, 1, n_+1)
            scanf("%s", Ls[i]+1);
            
        m_ = strlen(Ps[1]+1);
        tot = 0;
        s = m = 0;
        k = n_ * m_;
        t = k*2+1;
        memset(head, -1, sizeof(head));
        
        rep(i, 1, n_+1) {
            rep(j, 1, m_+1) {
                id = (i-1) * m_ + j;
                if (Ls[i][j] == 'L') {
                    addEdge(s, id, 1);
                    ++tot;
                }
                if (Ps[i][j] > '0') {
                    addEdge(id, id+k, Ps[i][j]-'0');
                    flag = true;
                    id += k;
                    rep(kk, 0, 4) {
                        x = i + dir[kk][0] * d;
                        y = j + dir[kk][1] * d;
                        if (x<=0 || x>n_ || y<=0 || y>m_) {
                            addEdge(id, t, INF);
                            flag = false;
                            break;
                        }
                    }
                    if (flag) {
                        id_ = 0;
                        rep(ii, 1, n_+1) {
                            rep(jj, 1, m_+1) {
                                ++id_;
                                tmp = abs(ii-i) + abs(jj-j);
                                if (tmp>0 && tmp<=d)
                                    addEdge(id, id_, Ps[i][j]-'0');
                            }
                        }
                    }
                }                
            }
        }
        
        ans = tot - Dinic(s, t);
        printf("Case #%d: ", tt);
        if (ans == 0) {
            printf("no lizard was left behind.
");
        } else if (ans == 1) {
            printf("1 lizard was left behind.
");
        } else {
            printf("%d lizards were left behind.
", ans);
        }
    }
    
    #ifndef ONLINE_JUDGE
        printf("time = %d.
", (int)clock());
    #endif
    
    return 0;
}