HDU 1421-move to dormitory

Question: When you move a dormitory, you can get up to two items at a time. The cost is the square of the difference in the weight of the items.

Analysis: DP, greedy. If two items are taken, the difference is the least square when the object is adjacent.

Proof: Set A <B <C <D: (expand)

(D-a) ^ 2 + (C-B) ^ 2> (D-C) ^ 2 + (B-a) ^ 2;

(D-B) ^ 2 + (c-a) ^ 2> (D-C) ^ 2 + (B-a) ^ 2;

With the above conclusion, you can directly sort the data by pressing "DP". You can get one or two values at a time.

Note ).

#include <stdio.h>#include <stdlib.h>#include <string.h>int W[ 2001 ];int F[ 2001 ][ 1001 ];int cmp( const void* a, const void* b ){    return (*(int *)a) - (*(int *)b);}int main(){    int n,k;    while ( ~scanf("%d%d",&n,&k) ) {        for ( int i = 1 ; i <= n ; ++ i )            scanf("%d",&W[ i ]);        qsort( &W[ 1 ], n, sizeof( int ), cmp );            memset( F, 0, sizeof( F ) );        for ( int i = 0 ; i <= n ; ++ i )        for ( int j = 1 ; j <= k ; ++ j )            F[ i ][ j ] = 0xffffff;                    for ( int i = 2 ; i <= n ; ++ i )        for ( int j = 1 ; j <= k && j <= i/2 ; ++ j ) {            if ( F[ i ][ j ] > F[ i-1 ][ j ] )                F[ i ][ j ] = F[ i-1 ][ j ];            int V = W[ i ] - W[ i-1 ];            if ( F[ i ][ j ] > F[ i-2 ][ j-1 ] + V*V )                F[ i ][ j ] = F[ i-2 ][ j-1 ] + V*V;        }                printf("%d\n",F[ n ][ k ]);    }    return 0;}

HDU 1421-move to dormitory