hdu1814 Peaceful Commission

hdu1814 Peaceful Commission

题意：2-sat裸题，打印字典序最小的

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我写了三个

1. 染色做法，正解
2. scc做法，不管字典序
3. scc做法，错误的字典序贪心

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
const int N = 2e4+5, M = 1e5+5;

inline int read() {
    int x = 0, f = 1; char c = getchar();
    while(c<'0' || c>'9') {if(c=='-') f=-1; c=getchar();}
    while(c>='0' && c<='9') {x=x*10+c-'0'; c=getchar();}
    return x * f;
}

int n, m;
struct edge {int v, ne;} e[M];
int cnt, h[N];
inline void ins(int u, int v) {
    e[++cnt] = (edge) {v, h[u]}; h[u] = cnt;
}
inline int id(int x) {return ((x-1)^1)+1;}
int col[N], st[N], top;
bool dfs(int u) {
    if(col[u]) return true;
    if(col[id(u)]) return false;
    col[u] = 1; st[top++] = u;
    for(int i=h[u]; i; i=e[i].ne) {
        int v = e[i].v;
        if(!dfs(v)) return false;
    }
    return true;
}
bool check(int u) {
    top = 1;
    return dfs(u);
}
int main() {
    freopen("in", "r", stdin);
    while(cin >> n) {
        cnt = 0;
        memset(h, 0, sizeof(h));
        memset(col, 0, sizeof(col));
        m = read();
        for(int i=1; i<=m; i++) {
            int a = read(), b = read();
            ins(a, id(b));
            ins(b, id(a));
        }
        int flag =  0;
        for(int i=1; i<=n<<1; i+=2) if(!col[i] && !col[id(i)]) {
            if(!check(i)) { 
                while(top) col[ st[top--] ] = 0;
                //for(int i=1; i<=n; i++) printf("col %d %d\n", i, col[i]);
                if(!check(id(i))) {
                    puts("NIE"), flag = 1;
                    break;
                }
            }
        }
        if(flag) continue;
        for(int i=1; i<=n<<1; i+=2) {
            if(col[i]) printf("%d\n", i);
            else printf("%d\n", i+1);
        }
    }
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
const int N = 2e4+5, M = 1e5+5;

inline int read() {
    int x = 0, f = 1; char c = getchar();
    while(c<'0' || c>'9') {if(c=='-') f=-1; c=getchar();}
    while(c>='0' && c<='9') {x=x*10+c-'0'; c=getchar();}
    return x * f;
}

int n, m;
struct edge {int v, ne;} e[M];
int cnt, h[N];
inline void ins(int u, int v) {
    e[++cnt] = (edge) {v, h[u]}; h[u] = cnt;
}
int dfn[N], dfc, scc, belong[N], low[N];
int st[N], top;
void dfs(int u) {
    dfn[u] = low[u] = ++dfc;
    st[++top] = u;
    for(int i=h[u]; i; i=e[i].ne) {
        int v = e[i].v;
        if(!dfn[v]) {
            dfs(v);
            low[u] = min(low[u], low[v]);
        } else if(!belong[v]) low[u] = min(low[u], dfn[v]);
    }
    if(dfn[u] == low[u]) {
        scc++;
        while(true) {
            int x = st[top--];
            belong[x] = scc;
            if(x == u) break;
        }
    }
}
namespace G {
    edge e[M];
    int cnt, h[N], ind[N];
    inline void ins(int u, int v) {
        e[++cnt] = (edge) {v, h[u]}; h[u] = cnt;
        ind[v] ++;
    }
    int q[N], head = 1, tail = 1;
#define pii pair<int, int>
#define fir first
#define sec second
    //priority_queue<pii, vector<pii>, greater<pii> > q;
    int col[N], opp[N];
    void dfs_color(int u) {
        if(col[u]) return;
        col[u] = -1;
        for(int i=h[u]; i; i=e[i].ne) dfs_color(e[i].v);
    }
    bool check() {
        for(int i=1; i<=n; i++) if(belong[i] == belong[i+n]) return false;
        return true;
    }
    void topo_sort() {
        head = tail = 1;
        for(int i=1; i<=scc; i++) if(!ind[i]) q[tail++] = i;
        while(head != tail) {
            int u = q[head++]; printf("uuu %d %d\n", u, col[u]);
            if(col[u]) continue;
            col[u] = 1; 
            dfs_color(opp[u]);
            for(int i=h[u]; i; i=e[i].ne) {
                int v = e[i].v;
                ind[v] --;
                if(ind[v] == 0) q[tail++] = v;
            }
        }
    }
}
int main() {
    freopen("in", "r", stdin);
    while(cin >> n) {
        m = read();
        for(int i=1; i<=m; i++) {
            int a = read(), b = read();
            ins(a, b+n);
            ins(b, a+n);
        }
        for(int i=1; i<=n<<1; i++) if(!dfn[i]) dfs(i);
        if(!G::check()) {
            puts("NIE");
            continue;
        }
        for(int u=1; u<=n<<1; u++) {
            int a = belong[u];
            for(int i=h[u]; i; i=e[i].ne) {
                int b = belong[e[i].v];
                if(a != b) ins(b, a);
            }
        }
        for(int i=1; i<=n; i++) {
            int a = belong[2*i-1], b = belong[2*i];
            G::opp[a] = b;
            G::opp[b] = a;
            printf("hi %d   %d %d\n", i, belong[a], belong[b]);
        }
        G::topo_sort();
        for(int i=1; i<=n<<1; i++)
            if(G::col[belong[i]] == 1) printf("%d\n", i);
    }
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
const int N = 2e4+5, M = 1e5+5;

inline int read() {
    int x = 0, f = 1; char c = getchar();
    while(c<'0' || c>'9') {if(c=='-') f=-1; c=getchar();}
    while(c>='0' && c<='9') {x=x*10+c-'0'; c=getchar();}
    return x * f;
}

int n, m;
struct edge {int v, ne;} e[M];
int cnt, h[N];
inline void ins(int u, int v) {
    e[++cnt] = (edge) {v, h[u]}; h[u] = cnt; 
}
int dfn[N], dfc, scc, belong[N], low[N];
int st[N], top;
void dfs(int u) { //printf("dfs %d\n", u);
    dfn[u] = low[u] = ++dfc;
    st[++top] = u;
    for(int i=h[u]; i; i=e[i].ne) {
        int v = e[i].v;
        if(!dfn[v]) {
            dfs(v);
            low[u] = min(low[u], low[v]);
        } else if(!belong[v])
            low[u] = min(low[u], dfn[v]);
    }
    if(dfn[u] == low[u]) {
        scc++;
        while(true) {
            int x = st[top--];
            belong[x] = scc;
            if(x == u) break;
        }
    }
}
inline int id(int x) {
    int t = ((x-1) >> 1) + 1;
    if(x == t<<1) return x-1;
    else return x+1;
}
int mn[N];
namespace G {
    edge e[M];
    int cnt, h[N], ind[N];
    inline void ins(int u, int v) {
        e[++cnt] = (edge) {v, h[u]}; h[u] = cnt;
        ind[v] ++;
    }
    //int q[N], head = 1, tail = 1;
#define pii pair<int, int>
#define fir first
#define sec second
    priority_queue<pii, vector<pii>, greater<pii> > q;
    int col[N], opp[N];
    void dfs_color(int u) {
        if(col[u]) return;
        col[u] = -1;
        for(int i=h[u]; i; i=e[i].ne) dfs_color(e[i].v);
    }
    bool check() {
        for(int i=1; i<=n; i++) if(belong[(i<<1)-1] == belong[i<<1]) return false;
        return true;
    }
    void topo_sort() {
        for(int i=1; i<=scc; i++) if(!ind[i]) q.push(make_pair(mn[i], i));
        while(!q.empty()) {
            int u = q.top().sec; q.pop(); printf("uuu %d  %d\n", u, mn[u]);
            if(col[u]) continue;
            col[u] = 1; 
            dfs_color(opp[u]);
            for(int i=h[u]; i; i=e[i].ne) {
                int v = e[i].v;
                ind[v] --;
                if(ind[v] == 0) q.push(make_pair(mn[v], v));
            }
        }
    }
}
int main() {
    freopen("in", "r", stdin);
    while(cin >> n) {
        memset(dfn, 0, sizeof(dfn));
        memset(low, 0, sizeof(low));
        memset(belong, 0, sizeof(belong));

        dfc = scc = 0;
        cnt = 0; G::cnt = 0;
        memset(h, 0, sizeof(h));
        memset(G::h, 0, sizeof(G::h));
        memset(G::col, 0, sizeof(G::col));
        memset(G::ind, 0, sizeof(G::ind));
        memset(mn, 0x3f, sizeof(mn));

        m = read();
        for(int i=1; i<=m; i++) {
            int a = read(), b = read();
            ins(a, id(b));
            ins(b, id(a));
            //printf("id %d %d\n", id(a), id(b));
        }
        for(int i=1; i<=n<<1; i++) if(!dfn[i]) dfs(i);
        if(!G::check()) {
            puts("NIE");
            continue;
        }
        for(int u=1; u<=n<<1; u++) {
            int a = belong[u];
            mn[a] = min(mn[a], u);
            for(int i=h[u]; i; i=e[i].ne) {
                int b = belong[e[i].v];
                if(a != b) G::ins(b, a);
            }
        }
        //for(int i=1; i<=n<<1; i++) printf("belong %d %d  %d\n", i, belong[i], mn[belong[i]]);
        for(int i=1; i<=n; i++) {
            int a = belong[(i<<1)-1], b = belong[i<<1];
            G::opp[a] = b;
            G::opp[b] = a;
            //printf("hi %d   %d %d\n", i, belong[a], belong[b]);
        }
        G::topo_sort();
        //for(int i=1; i<=n<<1; i++) printf("col %d %d  %d\n", i, belong[i], G::col[i]);
        for(int i=1; i<=n<<1; i+=2) {
            if(G::col[belong[i]] == 1) printf("%d\n", i);
            else printf("%d\n", id(i));
        }
    }
}

来源：https://www.cnblogs.com/candy99/p/9279525.html