POJ3278-Catch That Cow

典型的宽搜入门题。

注意边界条件。

#include <cstdio>#include <queue>#include <utility>using namespace std;const int MAX_N = 100000;typedef pair<int, int> P;queue<P> q;bool vis[MAX_N+1];int Bfs(int n, int k){    bool find_ans = false;    q.push(P(n, 0));    P cur;    while (!q.empty()) {        cur = q.front();        q.pop();        if (cur.first == k) {            find_ans = true;            break;        }                if (cur.first + 1 >= 0 && cur.first + 1 <= MAX_N && vis[cur.first+1] == false) {            q.push(P(cur.first+1, cur.second+1));            vis[cur.first+1] = true;        }        if (cur.first - 1 >= 0 && cur.first - 1 <= MAX_N && vis[cur.first-1] == false) {            q.push(P(cur.first-1, cur.second+1));            vis[cur.first-1] = true;        }        if (cur.first * 2 >= 0 && cur.first * 2 <= MAX_N && vis[cur.first*2] == false) {            q.push(P(cur.first*2, cur.second+1));            vis[cur.first*2] = true;        }    }        if (find_ans) {        return cur.second;    }    else        return -1;}int main(){    int n, k;    scanf("%d%d", &n, &k);        printf("%d\n", Bfs(n, k));        return 0;}