uva 10123 - No Tipping dp 记忆化搜索

这题的题意是 在双脚天平上有N块东西，依次从上面取走一些，最后使得这个天平保持平衡！

解题：

　　逆着来依次放入，如果可行那就可以，记得得有木板自身的重量。

/*************************************************************************
    > File Name: 10123.cpp
    > Author: opas
    > Mail: 1017370773@qq.com
    > Created Time: 2016年10月22日 星期六 22时58分53秒
 ************************************************************************/
#include<cstdio>
#include<string.h>
#include<algorithm>
#include<iostream>
using namespace std;
const int maxm = ;
const int maxn = <<maxm;
struct Node {
    int id,weight,dist;
    Node (int l_id = , int l_weight = , int l_dist = )    {
        id = l_id;
        weight = l_weight;
        dist = l_dist;
    }
    bool operator < (const Node A)const {
        if (weight != A.weight ) return weight < A.weight;
        return id < A.id;
    }
}package[maxm];
int dp[maxn];
int weight_val[maxn][];
int ans[maxm];
void InitVal(int n)    {
    int max_val = <<n;
    for(int i = ; i < max_val; ++ i)    {
        dp[i] = ;
    }
}
int length ,weight, num_package;
void AddPackage(int per_status ,int now_status, int id)    {
    for ( int i = ; i < ; ++ i)
        weight_val[now_status][i] = weight_val[per_status][i];
    if(package[id].dist <= -)    {
        weight_val[now_status][] = weight_val[per_status][] + - ( package[id].dist + ) * package[id].weight;
        weight_val[now_status][] = weight_val[per_status][] + - ( package[id].dist - ) * package[id].weight;
    }else if(package[id].dist < ){
        weight_val[now_status][] = weight_val[per_status][] + (package[id].dist + ) * package[id].weight;
        weight_val[now_status][] = weight_val[per_status][] + - (package[id].dist - ) * package[id].weight;
    }else{
        weight_val[now_status][] = weight_val[per_status][] + (package[id].dist + )*package[id].weight;
        weight_val[now_status][] = weight_val[per_status][] + (package[id].dist - )*package[id].weight;
    }
}
int CheckPackage(int now_status)    {
    int l_val1 = weight_val[now_status][];
    int l_val2 = weight_val[now_status][] + * weight;
    if(l_val1 > l_val2){
      return dp[now_status] = ;
    }
    l_val1 = weight_val[now_status][];
    l_val2 = weight_val[now_status][] +  * weight;
    if(l_val1 > l_val2) {
        return dp[now_status] = ;
    }
        return dp[now_status] = ;
}
int dfs(int now_loc, int now_status)    {
    if(now_loc == num_package)    {
        return ;
    }
    dp[now_status] = ;
    for(int i = ; i< num_package ; ++ i)    {
        if(now_status & (<<i))
            continue;
        int next_status = now_status | (<<i);
        if(dp[next_status] == ) return dp[next_status];
        AddPackage(now_status, next_status, i);
        if(CheckPackage(next_status) == )
            continue;
        ans[now_loc] = i;
        if (dfs(now_loc+, next_status) == )    {
            return dp[now_status]=;
        }
    }
    return ;
}
int main(){
    for(int cc = ; ; ++ cc) {
        cin>>length>>weight>>num_package;
        if(length + weight + num_package == )
                break;
        InitVal(num_package);
        for(int i = ; i < num_package; ++ i)    {
            int l_weight , l_dist;
            scanf("%d%d",&l_dist, &l_weight);
            l_dist = l_dist * ;
            package[i] = Node(i, l_weight, l_dist);
        }
        printf("Case %d:\n",cc);
        if( dfs( , ) == ) {
            for(int i = num_package - ; i >= ; -- i)    {
                printf("%d %d\n", package[ans[i]].dist/, package[ans[i]].weight);
            }
        }else{
            printf("Impossible\n");
        }
    }
    return ;
}