HDU-5543 DP

题目

Pick The Sticks

题解

01背包的加强版，由于两端可以放置 length/2 长度的木棍，所以加一维长度为3的状态，分别表示两端不放木棍，只有一端放木棍，两端都放木棍。

代码

#include <algorithm>
#include <bitset>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <climits>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
using namespace std;

const int MAX= 1005;
const int MAXN = 4005;

int len[MAX];
long long value[MAX];
long long dp[MAXN][3];

int main(){
    int T;
    cin >> T;
    for(int t=1;t<=T;++t){
        memset(dp,0,sizeof(dp));
        int n,l;
        cin >> n >> l;
        l *= 2;
        long long mx = 0;
        for (int i = 0; i < n; ++i) {
            scanf("%d %lld",len + i, value + i);
            len[i] *= 2;
            mx = max(mx, value[i]);
        }

        for (int i = 0; i < n; ++i){
            for (int j = l; j >= len[i]/2; --j) {
                for(int k=0;k<3;++k){
                    if(j >= len[i])
                        dp[j][k] = max(dp[j][k], dp[j - len[i]][k] + value[i]);
                    if(k > 0)
                        dp[j][k] = max(dp[j][k], dp[j - len[i] / 2][k-1] + value[i]);
                    mx = max(mx, dp[j][k]);
                }
            }
        }

        cout << "Case #" << t << ": " << mx << endl;

    }

    return 0;
}