UVa 11300 - Spreading the Wealth

/*
ch1, 例题3
代数分析 + 快速选择
*/
#include 
#include 
#include 

using namespace std;
const int MAXN = 1000004;
long long A[MAXN], B[MAXN];
int n;

int part(int x, int y)
{
    int i=x-1, j;
    long long key = B[y-1];
    for(j=x; j n/2) return get_mid(x, m);
    else return get_mid(m+1, y);
}

int main()
{
    #ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    #endif // ONLINE_JUDGE
    while(scanf("%d", &n) == 1) {
        long long tot = 0, m, x1, ans = 0;
        for(int i=1; i<=n; i++) {
            scanf("%lld", &A[i]);
            tot += A[i];
        }
        m = tot / n;
        B[0] = 0;
        for(int i=1; i