UVa 624

题意：

是找到和给出的分钟数相加最长的，但不长于所给的分钟数N。

思路：

01背包，加路径跟踪。

#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;

int N,tracksNum,tracks[22];
int bags[50030];
bool visit[50030][22];

void init();
void compu();
void output();
int main()
{
    #ifndef ONLINE_JUDGE
        freopen("D:\acm.txt","r",stdin);
    #endif // ONLINE_JUDGE
    compu();
    return 0;
}


void init(){
    memset(bags,0,sizeof(bags));
    memset(tracks,0,sizeof(tracks));
    memset(visit,false,sizeof(visit));
}

void output(){
    for(int i = tracksNum - 1,j = N;i >= 0;i--){//输出路径
        if(visit[j][i]){
            cout << tracks[i]<<" ";
            j = j - tracks[i];
        }
    }
    cout<<"sum:"<<bags[N]<<endl;
}

void compu(){
    while(cin >> N){
        init();
        cin>>tracksNum;
        for(int i = 0;i < tracksNum;i++) cin>>tracks[i];
/////////////////////////////////////////
        for(int i = 0;i < tracksNum;i++){
            for(int j = N;j >= tracks[i];j--){
                if(bags[j] < bags[j - tracks[i]] + tracks[i]){
                    bags[j] = bags[j - tracks[i]] + tracks[i];
                    visit[j][i] = true;
                }
            }
        }
        ////////////////////
        output();
    }
}