USACO算法系列二十三——rockers

    题目：http://www.nocow.cn/index.php/Translate:USACO/rockers

    类似于多机调度问题，但是又不太一样，添加了一个有时间顺序。我采用的深度搜索加剪枝的方法。

 #include <iostream>#include <fstream>#define SIZE 21using namespace std;int song[SIZE]={0};int cd[SIZE] = {0};int n,t,m;int result = 0;//深度遍历void putrocker(int cindex, int sindex, int number){//剪枝，没有剪枝的话会超时if(number + n - sindex + 1 < result)return;if (sindex > n || cindex > m){result = result < number ? number : result;}else{//刻录这首歌if (cd[cindex] + song[sindex] > t){putrocker(cindex+1,sindex, number);}else{cd[cindex] += song[sindex];putrocker(cindex, sindex+1, number+1);cd[cindex] -= song[sindex];}//不刻录此歌putrocker(cindex, sindex+1, number);}}int main(){ifstream fin("rockers.in");ofstream fout("rockers.out");//输入数据fin >> n >> t >> m;for(int i =1; i <= n; i ++){fin >> song[i];}putrocker(1,1,0);fout << result << endl;return 0;}

    运行结果：

Executing... Test 1: TEST OK [0.000 secs, 3016 KB] Test 2: TEST OK [0.011 secs, 3016 KB] Test 3: TEST OK [0.000 secs, 3016 KB] Test 4: TEST OK [0.011 secs, 3016 KB] Test 5: TEST OK [0.011 secs, 3016 KB] Test 6: TEST OK [0.011 secs, 3016 KB] Test 7: TEST OK [0.000 secs, 3016 KB] Test 8: TEST OK [0.054 secs, 3016 KB] Test 9: TEST OK [0.011 secs, 3016 KB] Test 10: TEST OK [0.000 secs, 3016 KB] Test 11: TEST OK [0.011 secs, 3016 KB] Test 12: TEST OK [0.000 secs, 3016 KB]All tests OK.

    后来看到别人使用动态规划的方法，令我叹为观止。我还是没办法像别人那样抽象的思考。