Submission #88878

#	Time	Username	Problem	Language	Result	Execution time	Memory
88878		sailormoon	Triumphal arch (POI13_luk)	C++14	90 / 100	1250 ms	38140 KiB

luk

#include <string>
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;
int canHandle(int v, int crs);
vector<vector<int>> graph (1000001); // size
bool visited[1000001];


int main() { 
    int n, a, b, start = 0, midpoint, end, cities; // n -> towns, a -> from, b -> to
    scanf("%d", &n);
    if (n == 0 || n == 1) {
        printf("%d\n", start);
        return 0;
    } 
    cities = n; // for further usage
    end = n; // last point
    n--;
    while (n--) {
        scanf("%d %d", &a, &b);
        graph[a].push_back(b);
        graph[b].push_back(a);
    }

    // binary search for sufficient amount of crews
    while (start < end) {
        midpoint = (start + end) / 2;
        for (int i = 0; i < cities; i++) visited[i] = false; // clear array 
        if (canHandle(1, midpoint) == 0) 
            end = midpoint;
        else   
            start = midpoint + 1; 
    }
    // if (start == 1) start = 0;
    printf("%d\n", start);

    return 0;
}

int canHandle(int v, int crs) {
    int num_children = 0, need_crews = 0;

    visited[v] = true;

    for (int i = 0; i < graph[v].size(); i++) {
        if (!visited[graph[v][i]]) { 
            num_children++;
            need_crews += canHandle(graph[v][i], crs);
        }
    }
    return max(0, num_children + need_crews - crs);
}

Compilation message (stderr)

luk.cpp: In function 'int canHandle(int, int)':
luk.cpp:48:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for (int i = 0; i < graph[v].size(); i++) {
                     ~~^~~~~~~~~~~~~~~~~
luk.cpp: In function 'int main()':
luk.cpp:14:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
     ~~~~~^~~~~~~~~~
luk.cpp:23:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d %d", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10