bzoj3969 [WF2013]Low Power

传送门：http://www.lydsy.com/JudgeOnline/problem.php?id=3969

【题解】

二分答案x，贪心选取，如果选取了i个，有j对，那么要满足i<=2*j*k（不然有数就没位置放了）

# include <stdio.h>
# include <string.h>
# include <iostream>
# include <algorithm>
// # include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
const int M = 2e6 + ;
const int mod = 1e9+;

# define RG register
# define ST static

int n, k, N;
int a[M]; 

inline bool chk(int x) {
    int times = ;
    for (int i=; i<=N; ++i) {
        if(i- > *times*k) return false;
        if(i <= N && a[i+] - a[i] <= x) ++i, ++times;
        if(times == n) return ;
    }
    return false;
}

int main() {
    cin >> n >> k; N = *n*k;
    for (int i=; i<=N; ++i) scanf("%d", a+i);
    sort(a+, a+N+);
    int l = a[] - a[], r = 1e9, ans;
    while() {
        if(r-l <= ) {
            for (int i=l; i<=r; ++i) {
                if(chk(i)) {
                    ans = i;
                    break;
                }
            }
            break;
        }
        int mid = l+r>>;
        if(chk(mid)) r = mid;
        else l = mid;
    }
    cout << ans << endl;
    return ;
}