HDU - 1495 非常可乐 【BFS】

题目链接

http://acm.hdu.edu.cn/showproblem.php?pid=1495

思路

首先 如果可乐的体积 是奇数 那么是无解的

然后 如果能够得到两杯 都是一般容量的可乐 那么一定是装在 原来那个可乐被子 以及 大一点的杯子当中

要找最少步骤 容易知道 用 BFS

每次转移的状态有

s -> n s -> m n -> s n -> m m -> s m -> n

用 vis 标记 状态

最后如果满足条件 就return

当然 即使可乐体积是偶数 也有可能 是没有办法满足条件的 也就是要设置一个哨兵

AC代码

#include <cstdio>
#include <cstring>
#include <ctype.h>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <ctime>
#include <iostream>
#include <algorithm>
#include <deque>
#include <vector>
#include <queue>
#include <string>
#include <map>
#include <stack>
#include <set>
#include <numeric>
#include <sstream>
#include <iomanip>
#include <limits>

#define CLR(a) memset(a, 0, sizeof(a))
#define pb push_back

using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef pair<string, int> psi;
typedef pair<string, string> pss;

const double PI = acos(-1);
const double E = exp(1);
const double eps = 1e-30;

const int INF = 0x3f3f3f3f;
const int maxn = 1e2 + 5;
const int MOD = 1e9 + 7;

struct node
{
    int s, n, m, t;
};

int s, n, m;

int vis[maxn][maxn];

int bfs()
{
    queue <node> q;
    CLR(vis);
    node temp;
    temp.s = s;
    temp.n = 0;
    temp.m = 0;
    temp.t = 0;
    vis[n][m] = 1;
    q.push(temp);
    while (!q.empty())
    {
        node u = q.front(), v;
        q.pop();
        if (u.n == s / 2 && u.s == s / 2)
            return u.t;
        if (u.s && u.n != n) // s -> n
        {
            int c = n - u.n;
            if (u.s >= c)
            {
                v.s = u.s - c;
                v.n = n;
            }
            else
            {
                v.s = 0;
                v.n = u.n + u.s;
            }
            v.m = u.m;
            if (vis[v.n][v.m] == 0)
            {
                v.t = u.t + 1;
                q.push(v);
                vis[v.n][v.m] = 1;
            }
        }
        if (u.s && u.m != m)  // s -> m
        {
            int c = m - u.m;
            if (u.s >= c)
            {
                v.s = u.s - c;
                v.m = m;
            }
            else
            {
                v.s = 0;
                v.m = u.m + u.s;
            }
            v.n = u.n;
            if (vis[v.n][v.m] == 0)
            {
                v.t = u.t + 1;
                q.push(v);
                vis[v.n][v.m] = 1;
            }
        }
        if (u.n && u.s != s) // n -> s
        {
            int c = s - u.s;
            if (u.n >= c)
            {
                v.n = u.n - c;
                v.s = s;
            }
            else
            {
                v.n = 0;
                v.s = u.s + u.n;
            }
            v.m = u.m;
            if (vis[v.n][v.m] == 0)
            {
                v.t = u.t + 1;
                q.push(v);
                vis[v.n][v.m] = 1;
            }
        }
        if (u.n && u.m != m) // n -> m
        {
            int c = m - u.m;
            if (u.n >= c)
            {
                v.n = u.n - c;
                v.m = m;
            }
            else
            {
                v.n = 0;
                v.m = u.m + u.n;
            }
            v.s = u.s;
            if (vis[v.n][v.m] == 0)
            {
                v.t = u.t + 1;
                q.push(v);
                vis[v.n][v.m] = 1;
            }
        }
        if (u.m && u.s != s) // m -> s
        {
            int c = s - u.s;
            if (u.m >= c)
            {
                v.m = u.m - c;
                v.s = s;
            }
            else
            {
                v.m = 0;
                v.s = u.s + u.m;
            }
            v.n = u.n;
            if (vis[v.n][v.m] == 0)
            {
                v.t = u.t + 1;
                q.push(v);
                vis[v.n][v.m] = 1;
            }
        }
        if (u.m && u.n != n) // m -> n
        {
            int c = n - u.n;
            if (u.m >= c)
            {
                v.m = u.m - c;
                v.n = n;
            }
            else
            {
                v.m = 0;
                v.n = u.n + u.m;
            }
            v.s = u.s;
            if (vis[v.n][v.m] == 0)
            {
                v.t = u.t + 1;
                q.push(v);
                vis[v.n][v.m] = 1;
            }
        }
    }
    return 0;
}

int main()
{
    while (scanf("%d%d%d", &s, &n, &m) && (s || n || m))
    {
        if (s & 1)
            puts("NO");
        else
        {
            if (n < m)
                swap(n, m);
            int ans = bfs();
            if (ans)
                cout << ans << endl;
            else
                puts("NO");
        }
    }
}