Codeforces 1209F Koala and Notebook

#include<bits/stdc++.h>
#define fi first
#define se second
#define mk make_pair
#define PII pair<int, int>

using namespace std;

const int N = (int)1e6 + 7;
const int mod = (int)1e9 + 7;

int n, m, tot;
int d[N], ans[N];
vector<PII> G[N];
vector<int> G2[N][10];
vector<int> V;

void solve(int u, int v, int x) {
    V.clear();
    for(int i = x; i; i /= 10) {
        V.push_back(i % 10);
    }
    reverse(V.begin(), V.end());
    int cur = u;
    for(int i = 0; i < V.size(); i++) {
        if(i == (int)V.size() - 1) {
            G[cur].push_back(mk(V[i], v));
        }
        else {
            tot++;
            G[cur].push_back(mk(V[i], tot));
            cur = tot;
        }
    }
    cur = v;
    for(int i = 0; i < V.size(); i++) {
        if(i == (int)V.size() - 1) {
            G[cur].push_back(mk(V[i], u));
        }
        else {
            tot++;
            G[cur].push_back(mk(V[i], tot));
            cur = tot;
        }
    }
}

void dfs(vector<int> &P) {
    vector<int> V;
    for(int i = 0; i <= 9; i++) {
        V.clear();
        for(auto &u : P) {
            for(auto &v : G2[u][i]) {
                if(~ans[v]) continue;
                ans[v] = (1LL * ans[u] * 10 + i) % mod;
                V.push_back(v);
            }
        }
        if(V.size()) dfs(V);
    }
}

int main() {
    scanf("%d%d", &n, &m);
    tot = n;
    for(int i = 1; i <= m; i++) {
        int u, v;
        scanf("%d%d", &u, &v);
        solve(u, v, i);
    }
    for(int i = 1; i <= tot; i++) {
        d[i] = -1;
        ans[i] = -1;
    }
    d[1] = 0;
    queue<int> que;
    que.push(1);
    while(!que.empty()) {
        int u = que.front();
        que.pop();
        for(auto &e : G[u]) {
            int v = e.se, w = e.fi;
            if(d[v] == -1) {
                d[v] = d[u] + 1;
                G2[u][w].push_back(v);
                que.push(v);
            }
            else if(d[u] + 1 == d[v]) {
                G2[u][w].push_back(v);
            }
        }
    }
    ans[1] = 0;
    vector<int> V;
    V.push_back(1);
    dfs(V);
    for(int i = 2; i <= n; i++) {
        printf("%d\n", ans[i]);
    }
    return 0;
}

/*
*/