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NC24416. [USACO 2013 Nov G]No Change

描述

Farmer John is at the market to purchase supplies for his farm. He has in his pocket K coins (1 <= K <= 16), each with value in the range 1..100,000,000. FJ would like to make a sequence of N purchases (1 <= N <= 100,000), where the ith purchase costs c(i) units of money (1 <= c(i) <= 10,000). As he makes this sequence of purchases, he can periodically stop and pay, with a single coin, for all the purchases made since his last payment (of course, the single coin he uses must be large enough to pay for all of these). Unfortunately, the vendors at the market are completely out of change, so whenever FJ uses a coin that is larger than the amount of money he owes, he sadly receives no changes in return! 
Please compute the maximum amount of money FJ can end up with after making his N purchases in sequence. Output -1 if it is impossible for FJ to make all of his purchases.

输入描述

* Line 1: Two integers, K and N.

* Lines 2..1+K: Each line contains the amount of money of one of FJ's
coins.

* Lines 2+K..1+N+K: These N lines contain the costs of FJ's intended
purchases.

输出描述

* Line 1: The maximum amount of money FJ can end up with, or -1 if FJ
cannot complete all of his purchases.

示例1

输入:

3 6
12
15
10
6
3
3
2
3
7

输出:

12

说明:

INPUT DETAILS:
FJ has 3 coins of values 12, 15, and 10. He must make purchases in
sequence of value 6, 3, 3, 2, 3, and 7.

OUTPUT DETAILS:
FJ spends his 10-unit coin on the first two purchases, then the 15-unit
coin on the remaining purchases. This leaves him with the 12-unit coin.

原站题解

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C++14(g++5.4) 解法, 执行用时: 86ms, 内存消耗: 1384K, 提交时间: 2020-05-10 09:33:34

#include<bits/stdc++.h>
#define P pair<int,int>
#define ll long long
using namespace std;
const int MX=1e5+9;
ll sum[MX],c[MX],val;
int dp[MX],k,n;

int erfen(ll val,int l,int r){
    if( l>r )
        return r;
    int mid=(l+r)>>1;
    if( sum[mid]<=val )
        erfen(val,mid+1,r);
    else
        erfen(val,l,mid-1);
}

int main()
{
//    freopen("input.txt","r",stdin);
    scanf("%d %d",&k,&n);
    for( int i=0 ; i<k ; i++ )
        scanf("%lld",&c[i]);
    for( int i=1 ; i<=n ; i++ ){
        scanf("%lld",&val);
        sum[i]=sum[i-1]+val;
    }
    sum[n+1]=0x3f;
    ll ans=-1;
    for( int i=0 ; i<(1<<k) ; i++ ){
        ll s=0;
        for( int j=0 ; j<k ; j++ ){
            if( i&(1<<j) )
                dp[i]=max(dp[i],erfen(sum[dp[i^(1<<j)]]+c[j],dp[i^(1<<j)]+1,n));
            else
               s+=c[j];
        }
        if( dp[i]==n )
            ans=max(ans,s);
    }
    printf("%lld\n",ans);
    return 0;
}

C++(g++ 7.5.0) 解法, 执行用时: 42ms, 内存消耗: 7776K, 提交时间: 2023-07-27 21:08:21

#include<bits/stdc++.h>
using namespace std;
int dp[66005]={0},S[100005]={0},pos[20][100005];
int main(){
	int i,j,k,n,l,r,a[20];
	long long s,ans=-1;
	scanf("%d%d",&k,&n);
	for(i=0;i<k;i++)
		scanf("%d",&a[i]);
    for(i=1;i<=n;i++)
		scanf("%d",&j),S[i]=S[i-1]+j;
    for(i=0;i<k;i++){
        for(l=r=n;l>=0;l--){
            while(S[r]-S[l]>a[i])
				r--;
            pos[i][l]=r;
        }
    }
    for(i=0;i<(1<<k);i++){
        for(j=0;j<k;j++){
            if((1<<j)&i)
				continue;
            dp[i|(1<<j)]=max(dp[i|(1<<j)],pos[j][dp[i]]);
        }
        if(dp[i]==n){
            for(s=j=0;j<k;j++)
				if(((1<<j)&i)==0)
					s+=a[j];
            ans=max(ans,s);
        }
    }
    printf("%lld\n",ans);
	return 0;
}

C++(clang++11) 解法, 执行用时: 33ms, 内存消耗: 7288K, 提交时间: 2021-04-07 16:57:26

#include<bits/stdc++.h>
using namespace std;

int DP[66005]={0},S[100005]={0},pos[20][100005];
int main()
{
	int i,j,n,m,l,r,a[20];
	long long s,ans=-1;
	scanf("%d%d",&m,&n);
	for(i=0;i<m;i++)scanf("%d",&a[i]);
	for(i=1;i<=n;i++)scanf("%d",&j),S[i]=S[i-1]+j;
	for(i=0;i<m;i++)
	{
		for(l=r=n;l>=0;l--)
		{
			while(S[r]-S[l]>a[i])r--;
			pos[i][l]=r;
		}
	}
	for(i=0;i<(1<<m);i++)
	{
		for(j=0;j<m;j++)
		{
			if((1<<j)&i)continue;
			DP[i|(1<<j)]=max(DP[i|(1<<j)],pos[j][DP[i]]);
		}
		if(DP[i]==n)
		{
			for(s=j=0;j<m;j++)if(((1<<j)&i)==0)s+=a[j];
			ans=max(ans,s);
		}
	}
	printf("%lld\n",ans);
	return 0;
}

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