Sicily 4428. How Many Sets

鉴于数据量比较小，直接使用递归省时省事（在敲代码方面）。往后递归，直至递归M次成功就是一个题目要求的子集。

Run Time: 0sec

Run Memory: 304KB

Code length: 599Bytes

Submit Time: 2011-12-14 00:17:49

// Problem#: 4428
// Submission#: 1074713
// The source code is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
// URI: http://creativecommons.org/licenses/by-nc-sa/3.0/
// All Copyright reserved by Informatic Lab of Sun Yat-sen University
#include<cstdio>
using namespace std;

int count;
int N, M;

void F( int n, int m ) {
    if ( m == M )
        count++;
    else {
        for ( int i = 2; n + i + 2 * ( M - m - 1 ) <= N; i++ )
            F( n + i, m + 1 );
    }
}

int main()
{
    int T;

    scanf( "%d", &T );
    while ( T-- ) {
        scanf( "%d%d", &N, &M );
        if ( M == 0 )
            printf( "1\n" );
        else {
            count = 0;
            for ( int i = 1; i <= N; i++ )
                F( i, 1 );
            printf( "%d\n", count );
        }
    }

    return 0;

}