Submission #92921

#	Time	Username	Problem	Language	Result	Execution time	Memory
92921		Flying_dragon_02	007 (CEOI14_007)	C++14	100 / 100	325 ms	17248 KiB

007

#include <bits/stdc++.h>

using namespace std;

#define fi first
#define se second
#define pb push_back
#define mp make_pair

typedef pair<int, int> ii;

const int N = 2e5 + 5;

int n, m, s, d, a, b, dista[N], distb[N], dist[N];

vector<int> graph[N];

queue<int> q;

int get(int f) {
    int res = 0;
    for(int i = 1; i <= N - 5; i++)
        dist[i] = N;
    dist[f] = 0;
    q.push(f);
    while(!q.empty()) {
        int u = q.front();
        q.pop();
        res = max(res, dist[u]);
        for(int i = 0; i < graph[u].size(); i++) {
            int v = graph[u][i];
            if(dist[v] > dist[u] + 1 && dista[v] + 1 == dista[u] && distb[v] + 1 == distb[u]) {
                dist[v] = dist[u] + 1;
                q.push(v);
            }
        }
    }
    return res;
}

int main() {
    //freopen("test.inp", "r", stdin);
    scanf("%d%d", &n, &m);
    scanf("%d%d%d%d", &s, &d, &a, &b);
    for(int i = 1; i <= m; i++) {
        int u, v;
        scanf("%d%d", &u, &v);
        graph[u].pb(v);
        graph[v].pb(u);
    }
    for(int i = 1; i <= N - 5; i++) {
        dista[i] = N;
        distb[i] = N;
    }
    dista[a] = 0;
    q.push(a);
    while(!q.empty()) {
        int u = q.front();
        q.pop();
        for(int i = 0; i < graph[u].size(); i++) {
            int v = graph[u][i];
            if(dista[v] > dista[u] + 1) {
                dista[v] = dista[u] + 1;
                q.push(v);
            }
        }
    }
    distb[b] = 0;
    q.push(b);
    while(!q.empty()) {
        int u = q.front();
        q.pop();
        for(int i = 0; i < graph[u].size(); i++) {
            int v = graph[u][i];
            if(distb[v] > distb[u] + 1) {
                distb[v] = distb[u] + 1;
                q.push(v);
            }
        }
    }
    int w1 = dista[d] - dista[s], w2 = distb[d] - distb[s];
    if(min(w1, w2) < 0) {
        printf("-1");
        exit(0);
    }
    int ans;
    if(w1 != w2) {
        printf("%d", min(w1, w2));
        exit(0);
    }
    else {
        int lmaoa = get(s), lmaob = get(d);
        if(lmaoa + w1 >= lmaob)
            ans = w1;
        else
            ans = w1 - 1;
    }
    if(ans < 0)
        printf("-1");
    else
        printf("%d", ans);
}

Compilation message (stderr)

007.cpp: In function 'int get(int)':
007.cpp:30:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < graph[u].size(); i++) {
                        ~~^~~~~~~~~~~~~~~~~
007.cpp: In function 'int main()':
007.cpp:60:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < graph[u].size(); i++) {
                        ~~^~~~~~~~~~~~~~~~~
007.cpp:73:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < graph[u].size(); i++) {
                        ~~^~~~~~~~~~~~~~~~~
007.cpp:43:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~
007.cpp:44:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d", &s, &d, &a, &b);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
007.cpp:47:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &u, &v);
         ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70