• hdu1814 Peaceful Commission


    hdu1814 Peaceful Commission

    题意:2-sat裸题,打印字典序最小的


    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
    ", 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
    ", i);
    			else printf("%d
    ", 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
    ", 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
    ", i, belong[a], belong[b]);
    		}
    		G::topo_sort();
    		for(int i=1; i<=n<<1; i++)
    			if(G::col[belong[i]] == 1) printf("%d
    ", 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
    ", 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
    ", 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
    ", 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
    ", 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
    ", i, belong[a], belong[b]);
    		}
    		G::topo_sort();
    		//for(int i=1; i<=n<<1; i++) printf("col %d %d  %d
    ", i, belong[i], G::col[i]);
    		for(int i=1; i<=n<<1; i+=2) {
    			if(G::col[belong[i]] == 1) printf("%d
    ", i);
    			else printf("%d
    ", id(i));
    		}
    	}
    }
    
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  • 原文地址:https://www.cnblogs.com/candy99/p/9279525.html
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