Submission #538174

#	Time	Username	Problem	Language	Result	Execution time	Memory
538174		79brue	Mountains and Valleys (CCO20_day1problem3)	C++14	0 / 25	5 ms	696 KiB

Main

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int n, m;
int dist[22][22];

int DP[1048576][20];
vector<int> link[5002];
queue<pair<int, int> > que;
bool visited[5002];

int main(){
    scanf("%d %d", &n, &m);
    if(n>3){
        for(int i=1; i<=m; i++){
            int x, y, c;
            scanf("%d %d %d", &x, &y, &c);
            if(c==1){
                link[x].push_back(y);
                link[y].push_back(x);
            }
        }
        que.push(make_pair(1, 0));
        visited[1] = 1;

        int nxt = 0, dst=0;
        while(!que.empty()){
            auto tmp = que.front(); que.pop();
            nxt = tmp.first;
            dst = tmp.second;
            for(auto x: link[tmp.first]){
                if(visited[x]) continue;
                visited[x] = 1;
                que.push(make_pair(x, tmp.second+1));
            }
        }

        memset(visited, 0, sizeof(visited));
        nxt = dst = 0;
        que.push(make_pair(nxt, 0));
        visited[nxt] = 1;
        while(!que.empty()){
            auto tmp = que.front(); que.pop();
            nxt = tmp.first;
            dst = tmp.second;
            for(auto x: link[tmp.first]){
                if(visited[x]) continue;
                visited[x] = 1;
                que.push(make_pair(x, tmp.second+1));
            }
        }

        printf("%d", 2*n-2-dst);
        return 0;
    }

    for(int i=0; i<=n; i++){
        for(int j=0; j<=n; j++){
            dist[i][j] = 1e9;
        }
    }

    for(int i=1; i<=m; i++){
        int x, y, c;
        scanf("%d %d %d", &x, &y, &c);
        dist[x][y] = dist[y][x] = c;
    }

    for(int k=0; k<n; k++){
        for(int i=0; i<n; i++){
            for(int j=0; j<n; j++){
                dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
            }
        }
    }

    for(int i=0; i<(1<<n); i++) for(int j=0; j<=n; j++) DP[i][j] = 1e9;
    for(int i=0; i<n; i++) DP[(1<<i)][i] = 0;

    for(int d=1; d<(1<<n); d++){
        for(int i=0; i<n; i++){
            if((d>>i)&1){
//                printf("%d %d: %d\n", d, i, DP[d][i]);
                for(int j=0; j<n; j++){
                    DP[(d|(1<<j))][j] = min(DP[(d|(1<<j))][j], DP[d][i] + dist[i][j]);
                }
            }
        }
    }

    int ans = 1e9;
    for(int i=0; i<n; i++) ans = min(ans, DP[(1<<n)-1][i]);

    printf("%d", ans);
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:16:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   16 |     scanf("%d %d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~~
Main.cpp:20:18: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   20 |             scanf("%d %d %d", &x, &y, &c);
      |             ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:68:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   68 |         scanf("%d %d %d", &x, &y, &c);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 1
• Subtask 2: 0 / 2
• Subtask 3: 0 / 2
• Subtask 4: 0 / 6
• Subtask 5: 0 / 2
• Subtask 6: 0 / 3
• Subtask 7: 0 / 5
• Subtask 8: 0 / 4