백준 2644번 C++

#include <iostream>

#include <cstring>

#include <vector>

#include <queue>

using namespace std;

int peoplenum, firstpeople, secondpeople, linknum;

vector<pair<int, int>> v;

int countans[100];

int num,maxnum=987654321;

void bfs(void) {

queue<int> q;

q.push(firstpeople);

while (!q.empty()) {

int people = q.front();

q.pop();

if (people == secondpeople) {

cout << countans[secondpeople];

return;

}

for (int i = 0; i < v.size(); i++) {

if (v[i].first == people) {

if (countans[v[i].second] == 0) {

q.push(v[i].second);

countans[v[i].second] = countans[people] + 1;

}

}

}

}

cout << "-1";

return;

}

int main(void) {

cin >> peoplenum;

cin >> firstpeople >> secondpeople;

cin >> linknum;

memset(countans, 0, sizeof(countans));

for (int i = 0; i < linknum; i++) {

int parent, child;

cin >> parent >> child;

v.push_back(make_pair(parent, child));

v.push_back(make_pair(child, parent));

}

bfs();

}