oj.uz

Submission #56067

# Submission time Handle Problem Language Result Execution time Memory
56067 2018-07-09T18:21:28 Z gabrielsimoes One-Way Streets (CEOI17_oneway) C++17
100 / 100
 1996 ms 33732 KB 
#include <bits/stdc++.h>
using namespace std;

typedef pair<int,int> pii;

const int MAXN = 1e5+10, MAXL = 18;

int n, m, p;
vector<pii> edges;
vector<pii> requirements;
vector<int> gix[MAXN];

bool isFirst(int cur, int edge) {
    return cur == edges[edge].first;
}

int other(int cur, int edge) {
    if (isFirst(cur, edge)) return edges[edge].second;
    else return edges[edge].first;
}

bool isPartOfCycle[MAXN];
bool edgeUsed[MAXN];
int status[MAXN];
vector<pii> stk;
void dfsCycles(int cur, int inIx) {
    status[cur] = 1;
    stk.push_back({cur, inIx});

    for (int ix : gix[cur]) {
        if (edgeUsed[ix]) continue;
        edgeUsed[ix] = true;

        int nx = other(cur, ix);

        if (status[nx] == 0) {
            dfsCycles(nx, ix);
        } else if (status[nx] == 1) {
            isPartOfCycle[ix] = true;
            int i = stk.size();
            while (--i >= 0) {
                if (stk[i].first != nx)
                    isPartOfCycle[stk[i].second] = true;
                else
                    break;
            }
        } else {
            fprintf(stderr, "ERROR: dfsCycles visited vertex already out of stack.");
            exit(1);
        }
    }

    stk.pop_back();
    status[cur] = 2;
}

int uf[MAXN];
void reset() { for (int i = 0; i < MAXN; i++) uf[i] = i; }
int get(int i) { return uf[i] == i ? i : uf[i] = get(uf[i]); }
void join(int a, int b) { uf[get(b)] = get(a); }

enum Answer {UNDEFINED, LEFT, RIGHT, BOTH};
Answer ans[MAXN];

int parent[MAXN], depth[MAXN], edgeParent[MAXN];
void dfsLCA(int cur, int pre) {
    parent[cur] = pre;
    depth[cur] = depth[pre] + 1;
    status[cur] = 1;

    for (int ix : gix[cur]) {
        int nx = other(cur, ix);

        if (nx != pre) {
            // printf("%d->%d (%d)\n", cur,nx, ix);
            edgeParent[nx] = ix;
            dfsLCA(nx, cur);
        }
    }
}

int main() {
    scanf("%d %d", &n, &m);
    for (int i = 0,a,b; i < m; i++) {
        scanf("%d %d", &a, &b);
        edges.push_back({a,b});
        gix[a].push_back(i);
        gix[b].push_back(i);
    }

    scanf("%d", &p);
    for (int i = 0,a,b; i < p; i++) {
        scanf("%d %d", &a, &b);
        requirements.push_back({a,b});
    }

    for (int i = 1; i <= n; i++) {
        if (status[i] == 0) {
            dfsCycles(i, -1);
        }
    }

    reset();

    for (int i = 0; i < m; i++) {
        if (isPartOfCycle[i]) {
            ans[i] = BOTH;
            join(edges[i].first, edges[i].second);
        }
    }

    for (int i = 1; i <= n; i++) {
        gix[i].clear();
        status[i] = 0;
    }

    for (int i = 0; i < m; i++) {
        int a = get(edges[i].first), b = get(edges[i].second);
        edges[i] = {a, b};

        if (a != b) {
            gix[a].push_back(i);
            gix[b].push_back(i);

            // printf("new vertex: %d %d (%d)\n", a, b, i);
        }
    }

    for (int i = 1; i <= n; i++) {
        if (status[i] == 0) {
            dfsLCA(i, i);
        }
    }

    for (int i = 0; i < p; i++) {
        int a = get(requirements[i].first), b = get(requirements[i].second);

        while (a != b) {
            int da = depth[a], db = depth[b];

            // printf("%d (%d) %d (%d)\n", a, edgeParent[a], b, edgeParent[b]);

            if (da >= db) {
                ans[edgeParent[a]] = isFirst(a, edgeParent[a]) ? RIGHT : LEFT;
                join(parent[a], a);
                a = get(parent[a]);
            }

            if (db >= da) {
                ans[edgeParent[b]] = isFirst(b, edgeParent[b]) ? LEFT : RIGHT;
                join(parent[b], b);
                b = get(parent[b]);
            }
        }
    }

    for (int i = 0; i < m; i++) {
        switch(ans[i]) {
            case LEFT: printf("L"); break;
            case RIGHT: printf("R"); break;
            default: printf("B");
        }
    }

    printf("\n");
}

Compilation message

oneway.cpp: In function 'int main()':
oneway.cpp:83:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d", &n, &m);
     ~~~~~^~~~~~~~~~~~~~~~~
oneway.cpp:85:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~~
oneway.cpp:91:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &p);
     ~~~~~^~~~~~~~~~
oneway.cpp:93:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~~

Subtask #1
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 3064 KB Output is correct
2 Correct 4 ms 3204 KB Output is correct
3 Correct 5 ms 3240 KB Output is correct
4 Correct 5 ms 3316 KB Output is correct
5 Correct 4 ms 3360 KB Output is correct
6 Correct 4 ms 3360 KB Output is correct
7 Correct 6 ms 3368 KB Output is correct
8 Correct 5 ms 3368 KB Output is correct
9 Correct 5 ms 3368 KB Output is correct
10 Correct 4 ms 3496 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 3064 KB Output is correct
2 Correct 4 ms 3204 KB Output is correct
3 Correct 5 ms 3240 KB Output is correct
4 Correct 5 ms 3316 KB Output is correct
5 Correct 4 ms 3360 KB Output is correct
6 Correct 4 ms 3360 KB Output is correct
7 Correct 6 ms 3368 KB Output is correct
8 Correct 5 ms 3368 KB Output is correct
9 Correct 5 ms 3368 KB Output is correct
10 Correct 4 ms 3496 KB Output is correct
11 Correct 1350 ms 7996 KB Output is correct
12 Correct 1996 ms 9096 KB Output is correct
13 Correct 1908 ms 10176 KB Output is correct
14 Correct 1173 ms 11128 KB Output is correct
15 Correct 824 ms 11268 KB Output is correct
16 Correct 87 ms 11268 KB Output is correct
17 Correct 97 ms 11284 KB Output is correct
18 Correct 144 ms 11284 KB Output is correct
19 Correct 149 ms 12564 KB Output is correct
20 Correct 490 ms 12564 KB Output is correct
21 Correct 115 ms 12564 KB Output is correct

Subtask #3
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 3064 KB Output is correct
2 Correct 4 ms 3204 KB Output is correct
3 Correct 5 ms 3240 KB Output is correct
4 Correct 5 ms 3316 KB Output is correct
5 Correct 4 ms 3360 KB Output is correct
6 Correct 4 ms 3360 KB Output is correct
7 Correct 6 ms 3368 KB Output is correct
8 Correct 5 ms 3368 KB Output is correct
9 Correct 5 ms 3368 KB Output is correct
10 Correct 4 ms 3496 KB Output is correct
11 Correct 1350 ms 7996 KB Output is correct
12 Correct 1996 ms 9096 KB Output is correct
13 Correct 1908 ms 10176 KB Output is correct
14 Correct 1173 ms 11128 KB Output is correct
15 Correct 824 ms 11268 KB Output is correct
16 Correct 87 ms 11268 KB Output is correct
17 Correct 97 ms 11284 KB Output is correct
18 Correct 144 ms 11284 KB Output is correct
19 Correct 149 ms 12564 KB Output is correct
20 Correct 490 ms 12564 KB Output is correct
21 Correct 115 ms 12564 KB Output is correct
22 Correct 200 ms 12564 KB Output is correct
23 Correct 175 ms 12820 KB Output is correct
24 Correct 182 ms 15164 KB Output is correct
25 Correct 175 ms 21944 KB Output is correct
26 Correct 170 ms 21944 KB Output is correct
27 Correct 171 ms 22060 KB Output is correct
28 Correct 74 ms 22060 KB Output is correct
29 Correct 222 ms 24116 KB Output is correct
30 Correct 108 ms 26560 KB Output is correct
31 Correct 684 ms 29172 KB Output is correct
32 Correct 136 ms 33732 KB Output is correct