URAL 2089 Experienced coach Twosat

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <queue>
#include <stack>
#include <cstdlib>
#include <map>
#include <set>
#include <cmath>
using namespace std;
const int N = 2e6 + 100;
struct Edge {
    int to, nex;
}e[N];
int head[N], tot;
void init() {
    tot = 0; memset(head, -1, sizeof head);
}
void add(int u, int v) {
    e[tot].to = v;
    e[tot].nex = head[u];
    head[u] = tot++;
}
int Low[N], DFN[N], Stack[N], Belong[N];
int Index, top;
int scc;
bool Instack[N];
int num[N];

void Tarjan(int u) {
    int v;
    Low[u] = DFN[u] = ++Index;
    Stack[top++] = u;
    Instack[u] = true;

    for(int i = head[u]; ~i; i = e[i].nex) {
        v = e[i].to;
        if(!DFN[v]) {
            Tarjan(v);
            if(Low[u] > Low[v]) Low[u] = Low[v];
        }else if(Instack[v] && Low[u] > DFN[v]) Low[u] = DFN[v];
    }
    if(Low[u] == DFN[u]) {
        scc++;
        do
        {
            v = Stack[--top];
            Instack[v] = false;
            Belong[v] = scc;
            num[scc]++;
        }while(v != u);
    }
}
bool solvable(int n) {
    memset(DFN, 0, sizeof DFN);
    memset(Instack, false, sizeof Instack);
    memset(num, 0, sizeof num);
    Index = scc = top = 0;
    for(int i = 0; i < n; ++i) if(!DFN[i]) Tarjan(i);

    for(int i = 0; i < n; i += 2) {
        if(Belong[i] == Belong[i ^ 1]) return false;
    }
    return true;
}

queue<int> q1, q2;
vector<vector<int> >dag;
int vis[N];
int indeg[N];
int cf[N];
void solve(int n) {
    dag.assign(scc+1, vector<int>());
    memset(indeg, 0, sizeof indeg);
    memset(vis, 0, sizeof vis);
    for(int u = 0; u < n; ++u) {
        for(int i = head[u]; ~i; i = e[i].nex) {
            int v = e[i].to;
            if(Belong[u] != Belong[v]) {
                dag[ Belong[v] ].push_back(Belong[u]);
                indeg[ Belong[u] ]++;
            }
        }
    }
    for(int i = 0; i < n; i += 2) {
        cf[ Belong[i] ] = Belong[i ^ 1];
        cf[ Belong[i ^ 1] ] = Belong[i];
    }
    while(!q1.empty()) q1.pop();
    while(!q2.empty()) q2.pop();
    for(int i = 1; i <= scc; ++i) if(indeg[i] == 0) q1.push(i);

    while(!q1.empty()) {
        int u = q1.front();
        q1.pop();
        if(vis[u] == 0) {
            vis[u] = 1;
            vis[ cf[u] ] = 0;
        }
        int sz = dag[u].size();
        for(int i = 0; i < sz; ++i) {
            indeg[ dag[u][i] ]--;
            if(indeg[ dag[u][i] ] == 0) q1.push(dag[u][i]);
        }
    }
}
int r[N];
vector<int> g[N];
int main() {
#ifdef LOCAL
    freopen("in", "r", stdin);
#endif
    int n, m;
    while(~scanf("%d%d", &m, &n)) {
        init();
        int tot = 0; int u, v;
        for(int i = 0; i < m; ++i) {
            scanf("%d%d", &u, &v);
            r[tot++] = u;
            r[tot++] = v;
            g[u].push_back(2 * i);
            g[v].push_back(2 * i + 1);
        }

        for(int i = 1; i <= n; ++i) {
            int sx = g[i].size();
            for(int j1 = 0; j1 < sx; ++j1) {
                for(int j2 = j1 + 1; j2 < sx; ++j2) {
                    int v1 = g[i][j1];
                    int v2 = g[i][j2];
                    add(v1, v2 ^ 1);
                    add(v2, v1 ^ 1);
                }
            }
        }
        if(solvable(2 * m)) {
            solve(2 * m);
            puts("Yes");
            for(int i = 0; i < m; ++i) {
                if(vis[ Belong[2 * i] ]) printf("%d\n", r[2 * i + 1]);
                else printf("%d\n", r[2 * i]);
            }
        }else puts("No");
    }
    return 0;
}