Submission #408954

#	Time	Username	Problem	Language	Result	Execution time	Memory
408954		ly20	The Xana coup (BOI21_xanadu)	C++17	100 / 100	83 ms	20296 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 112345;
long long INF = 1123456789;
vector <int> grafo[MAXN];
int tp[MAXN];
long long dp[MAXN][2][2];
void dfs(int v, int p) {
    for(int i = 0; i < grafo[v].size(); i++) {
        int viz = grafo[v][i];
        if(viz == p) continue;
        dfs(viz, v);
    }
    long long cur[2][2];
    bool fl = 0;
    for(int i = 0; i < grafo[v].size(); i++) {
        int viz = grafo[v][i];
        if(viz == p) continue;
        //printf("%d\n", v);
        if(fl == 0) {
                //printf("%d\n", fl);
            cur[0][0] = dp[viz][0][0]; cur[0][1] = dp[viz][0][1];
            cur[1][0] = dp[viz][1][0]; cur[1][1] = dp[viz][1][1];
            fl = 1;
        }
        else {
                //printf("oi\n");
            long long temp[2][2];
            temp[0][0] = min(cur[0][0] + dp[viz][0][0], cur[0][1] + dp[viz][0][1]);
            temp[0][1] = min(cur[0][1] + dp[viz][0][0], cur[0][0] + dp[viz][0][1]);
            temp[1][0] = min(cur[1][0] + dp[viz][1][0], cur[1][1] + dp[viz][1][1]);
            temp[1][1] = min(cur[1][1] + dp[viz][1][0], cur[1][0] + dp[viz][1][1]);
            cur[0][0] = temp[0][0]; cur[0][1] = temp[0][1];
            cur[1][0] = temp[1][0]; cur[1][1] = temp[1][1];
            //printf("%d %d %d %d %d\n", v, temp[0][0], temp[0][1], temp[1][0], temp[1][1]);
        }
    }
    if(fl == 0) {
        //printf("%d\n", v);
        if(tp[v] == 0) {
                //printf("%d\n", v);
            dp[v][0][0] = 0LL;
            dp[v][0][1] = INF;
            dp[v][1][0] = INF;
            dp[v][1][1] = 1LL;
        }
        else {
            dp[v][0][0] = INF;
            dp[v][0][1] = 1LL;
            dp[v][1][0] = 0LL;
            dp[v][1][1] = INF;
        }
        //printf("%d %lld %lld %lld %lld\n", v, dp[v][0][0], dp[v][1][0], dp[v][0][1], dp[v][1][1]);
    }
    else {
        if(tp[v] == 0) {
            dp[v][0][0] = cur[0][0];
            dp[v][0][1] = cur[1][1] + 1;
            dp[v][1][0] = cur[0][1];
            dp[v][1][1] = cur[1][0] + 1;
        }
        else {
            dp[v][0][0] = cur[0][1];
            dp[v][0][1] = cur[1][0] + 1;
            dp[v][1][0] = cur[0][0];
            dp[v][1][1] = cur[1][1] + 1;
        }
    }
    //printf("%d %lld %lld %lld %lld\n", v, dp[v][0][0], dp[v][1][0], dp[v][0][1], dp[v][1][1]);
}
int main() {
    int n;
    scanf("%d", &n);
    for(int i = 0; i < n - 1; i++) {
        int a, b;
        scanf("%d %d", &a, &b);
        grafo[a].push_back(b); grafo[b].push_back(a);
    }
    for(int i = 1; i <= n; i++) scanf("%d", &tp[i]);
    dfs(1, 1);
    if(min(dp[1][0][0], dp[1][0][1]) < INF) printf("%lld\n", min(dp[1][0][0], dp[1][0][1]));
    else printf("impossible\n");
}

Compilation message (stderr)

xanadu.cpp: In function 'void dfs(int, int)':
xanadu.cpp:9:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
    9 |     for(int i = 0; i < grafo[v].size(); i++) {
      |                    ~~^~~~~~~~~~~~~~~~~
xanadu.cpp:16:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |     for(int i = 0; i < grafo[v].size(); i++) {
      |                    ~~^~~~~~~~~~~~~~~~~
xanadu.cpp: In function 'int main()':
xanadu.cpp:73:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   73 |     scanf("%d", &n);
      |     ~~~~~^~~~~~~~~~
xanadu.cpp:76:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   76 |         scanf("%d %d", &a, &b);
      |         ~~~~~^~~~~~~~~~~~~~~~~
xanadu.cpp:79:38: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |     for(int i = 1; i <= n; i++) scanf("%d", &tp[i]);
      |                                 ~~~~~^~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30