P2918 [USACO08NOV]买干草Buying Hay - 完全背包

枚举上界还是好确定的，至多买h + 5000磅干草，因为一捆干草至多重5000磅

#include 
#include 
#include 
#include 
using namespace std;
#define debug(x) cerr << #x << "=" << x << endl;
const int MAXN = 55000 + 10;
typedef long long ll;
int n,h,ans,sum,dp[MAXN],cost;
struct hays{
    int p, c;
}hay[MAXN];

int main() {
    cin >> n >> h;
    for(int i=1; i<=n; i++) {
        cin >> hay[i].p >> hay[i].c;
        cost = max(cost, hay[i].c);
    }
    memset(dp, 0x3f, sizeof(dp));
    dp[0] = 0;
    ans = 1<<30;
    for(int i=1; i<=n; i++) {
        for(int j=0; j <= h + 5000; j++) {
            if(j >= hay[i].p) {
                dp[j] = min(dp[j], dp[j-hay[i].p] + hay[i].c);
            }
            if(j >= h) {
                ans = min(ans, dp[j]);
            }
        }
    }
    cout << ans;
    // dp[i][j] Ç°i¸öÎïÆ·»¨·ÑΪjµÄ×î´óÖØÁ¿ 
    return 0;
}