poj 1882 Stamps 二维费用背包

//f[i][l][k]表示第i组数，话费l或l个以下的邮票可达到k价值 //f[i][l][k] = f[i][l][k] | f[i][l - 1][k - a[i][j]] || f[i][l - 1][k]; #include <iostream> #include <cmath> #include <cstring> #include <algorithm> using namespace std; bool f[10][11][1001]; int n; int d[10]; int a[10][10]; int _max[10]; int _maxIndex; int main() { //freopen("1.txt", "r", stdin); int s; while(cin >> s && s != 0) { cin >> n; for(int i = 0; i < n; i++) { cin >> d[i]; for(int j = 0; j < d[i]; j++) cin >> a[i][j]; } memset(f, false, sizeof(f)); for(int i = 0; i < n; i++) for(int j = 0; j <= s; j++) f[i][j][0] = true; for(int i = 0; i < n; i++) { int maxV = a[i][d[i] - 1] * s; for(int j = 0; j < d[i]; j++) { for(int l = 1; l <= s; l++) { //万恶的循环，题目的5迷惑。。。 for(int k = maxV; k >= a[i][j]; k--) { //f[i][l][k] = f[i][l][k] | f[i][l - 1][k - a[i][j]]; f[i][l][k] = f[i][l][k] | f[i][l - 1][k - a[i][j]] || f[i][l - 1][k]; } } } int j = 1; while(f[i][s][j]) j++; _max[i] = j - 1; if(i == 0) _maxIndex = 0; else if(_max[i] > _max[_maxIndex]) _maxIndex = i; else if(_max[i] == _max[_maxIndex]) { if(d[i] < d[_maxIndex]) _maxIndex = i; else if(d[i] == d[_maxIndex] && a[i][d[i] - 1] < a[_maxIndex][d[_maxIndex] - 1]) _maxIndex = i; } } cout << "max coverage = " << _max[_maxIndex] << " :"; for(int i = 0; i < d[_maxIndex]; i++) cout << " " << a[_maxIndex][i]; cout << endl; } return 0; } 

 

后来上网看到用完全背包的方法，自己尝试了一下，时间少了一半。。

//上网看的更优的算法：当作完全背包，最后看是否超过上限 //f[j]表示构成价值j的邮票所需最小的邮票数 #include <iostream> #include <cmath> #include <cstring> using namespace std; const int INF = 99999999; int f[1001]; int n; int s; int d[10]; int a[10][10]; int _max; int index; int main() { //freopen("1.txt", "r", stdin); while(cin >> s && s != 0) { cin >> n; _max = 0; index = 0; for(int i = 0; i < n; i++) { cin >> d[i]; for(int j = 0; j < d[i]; j++) cin >> a[i][j]; int _maxV = a[i][d[i] - 1] * s; for(int j = 0; j <= _maxV; j++) f[j] = INF; f[0] = 0; for(int j = 0; j < d[i]; j++) { for(int k = a[i][j]; k <= _maxV; k++) { f[k] = min(f[k], f[k - a[i][j]] + 1); } } int tmp = 0; for(; tmp <= _maxV; tmp++) if(f[tmp] > s) break; tmp--; if(tmp > _max) { _max = tmp; index = i; }else if(tmp == _max) { if(d[i] < d[index]) { _max = tmp; index = i; }else if(d[i] == d[index] && a[i][d[i] - 1] < a[index][d[index] - 1]) { _max = tmp; index = i; } } } cout << "max coverage = " << _max << " :"; for(int i = 0; i < d[index]; i++) cout << " " << a[index][i]; cout << endl; } return 0; }