[DP] [01] [洛谷] P1510 味精填海

基础01背包DP

考察对背包决策过程的理解

#pragma GCC optimize(2)
#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <cctype>
#include <string>
#include <cstring>
#include <algorithm>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <ctime>
#include <vector>
#include <fstream>
#include <list>
#include <iomanip>
#include <numeric>
using namespace std;
typedef long long ll;

const int MAXN = 1e6 + 10;

ll inf = -1;

ll v, n, c;

bool flag = false;

int dp[MAXN] = {0};

int volume[MAXN];

int value[MAXN];

ll ans = inf;

int main()
{
    ios::sync_with_stdio(false);

    cin.tie(0);     cout.tie(0);

    cin>>v>>n>>c;

    for(int i = 1; i <= n; i++)
    {
        cin>>value[i]>>volume[i];
    }

    for(int i = 1; i <= n; i++)
    {
        for(int j = c; j >= volume[i]; j--)
        {
            dp[j] = max(dp[j], dp[j - volume[i]] + value[i]);
            
            if(dp[j] >= v)
            {
                ans = max(ans, c - j);
                flag = true;
            }
        }
    }

    flag ? cout<<ans<<endl : cout<<"Impossible"<<endl ;

    return 0;
}