【二分】bestcoder p1m2

 1 #include<bits/stdc++.h>
 2 const int maxn = 300035;
 3 
 4 int T,n,ans,mx,mn,l,r;
 5 int a[maxn];
 6 
 7 int read()
 8 {
 9     char ch = getchar();
10     int num = 0;
11     bool fl = 0;
12     for (; !isdigit(ch); ch = getchar())
13         if (ch==‘-‘) fl = 1;
14     for (; isdigit(ch); ch = getchar())
15         num = (num<<1)+(num<<3)+ch-48;
16     if (fl) num = -num;
17     return num;
18 }
19 bool check(int x)
20 {
21     long long cnt = 0;
22     for (int i=1; i<=n; i++)
23         if (a[i] <= x) cnt += x-a[i];
24         else cnt -= (a[i]-x)/2;
25     return cnt <= 0;
26 }
27 int main()
28 {
29     T = read();
30     while (T--)
31     {
32         n = read(), ans = -1, mx = 0, mn = 2e9;
33         for (int i=1; i<=n; i++) a[i] = read(), mx = std::max(mx, a[i]), mn = std::min(mn, a[i]);
34         l = mn, r = mx;
35         for (int mid=(l+r)>>1; l<=r; mid=(l+r)>>1)
36             if (check(mid)) ans = mid, l = mid+1;
37             else r = mid-1;
38         printf("%d\n",ans);
39     }
40     return 0;
41 }