Hdu4546 -- DP/priority queue-many priority queue questions recently

I recently encountered many questions about the priority queue. Today, cf B is the priority queue. If the test is AC ..

The general practice of this question is to use the priority queue for many people.

However, I saw in discuss that using the DP decision-making backpack to do this kind of thinking is particularly good. I will talk about its ideas here. As for the priority queue, I will not bother to say it.

 

There is a code segment that is very core and we can use it later, as if I have not used it myself.

1         j=cnt=0,k=n;;2         while(cnt<q)3         {4             cnt+=k;5             j++;6             if (j==n)7                 break;8             k=(k*(n-j)/(j+1));9         }

That is to say, the final result is q <= the number of all combinations.

> = The front is the letter J.

1         for (m=0,i=n-1;j!=0;j--)2             m+=a[i--];

So here we will find the worst case to find out the greatest difficulty of J-Question.

1 memset (F, 0, sizeof (f); 2 F [0] = 1; // I modified 3 for (I = 0; I <N; I ++) 4 {5 for (j = m; j-A [I]> = 0; j --) 6 {// If (F [J-A [I]) 7 f [J] + = f [J-A [I] written by the original author; 8 // F [A [I] ++; 9 Written by the original author} 10} 11 F [0] = 0; // my modified

Here we can regard it as a 01 backpack. The F [x] array defines the number of solutions with difficulty <= x

Of course, in the above code, we can only find the number of solutions for F [x] When the difficulty is exactly X.

But it doesn't matter. We only need to traverse 1-m after the above code is executed and accumulate with recursion.

1         for (i=1;i<=m;i++)2             f[i]+=f[i-1];

Then you can compare my writing method with that of the original author. We are just a little different in initialization.

In fact, if you think about it, you will find that there is a bug in my program, that is, the input difficulty is not 0 by default ..

Then I went to ask for data with the HDU Admin. I had to give it to me in the hope of a try.

Then their data contains 0 and more than one group -.-

1 # include <iostream> 2 # include <queue> 3 # include <algorithm> 4 using namespace STD; 5 6 int n, m; 7 typedef long ll; 8 const int size = 11010; 9 LL arr [size]; 10 struct node11 {12 ll sum; 13 LL nextsum; 14 int nextid; 15 node (){}; 16 node (ll a, LL B, int C): sum (A), nextsum (B), nextid (c) {}; 17 bool operator <(const node & Q) const18 {19 Return nextsum> q. nextsum; // small first team: 20} 21}; 22 priority _ Queue <node> q; 23 24 ll solve () 25 {26 while (! Q. empty () 27 Q. pop (); 28 Q. push (node (0, arr [0], 0); 29 int CNT; 30 LL ans, VAR; 31 node now; 32 CNT = arr [N] = 0; 33 while (CNT <m) 34 {35 now = Q. top (); 36 Q. pop (); 37 Var = now. nextsum; 38 If (now. nextid> = N) 39 {40 continue; 41} 42 Q. push (node (now. sum, now. sum + arr [now. nextid + 1], now. nextid + 1); 43 Q. push (node (now. nextsum, now. nextsum + arr [now. nextid + 1], now. nextid + 1); 44 + + CNT; 45} 46 Return var; 47} 48 49 int main () 50 {51 cin. sync_with_stdio (false); 52 int t; 53 CIN> T; 54 LL ans; 55 for (int K = 1; k <= T; ++ K) 56 {57 CIN> N> m; 58 for (INT I = 0; I <n; ++ I) 59 {60 CIN> arr [I]; 61} 62 sort (ARR, arr + n); 63 ans = solve (); 64 cout <"case #" <k <": "<ans <Endl; 65} 66 return 0; 67}

View code

Paste the code of the priority queue. As for the backpack, you will be too lazy to paste it. You can see it in discuss.

 

Today:

Sometimes

You expect everything to be new

Sometimes

You expect everything to be as usual

Sometimes

You expect everything to be old

However

Past and future cannot go now

 

Hdu4546 -- DP/priority queue-many priority queue questions recently