题目传送门
1 /*
2 二分搜索：在0～1e6的范围找到最小的max (ai - bi)，也就是使得p + 1 <= a[i] + c or a[i] - c
3 比赛时以为是贪心，榨干智商也想不出来:(
4 */
5 #include <cstdio>
6 #include <algorithm>
7 #include <cstring>
8 #include <cmath>
9 #include <iostream>
10 using namespace std;
11
12 const int MAXN = 1e5 + 10;
13 const int INF = 0x3f3f3f3f;
14 int a[MAXN];
15 int n;
16
17 bool check(int c)
18 {
19 int p = -1e6;
20 for (int i=1; i<=n; ++i)
21 {
22 int now = max (p + 1, a[i] - c);
23 if (now > a[i] + c) return false;
24 p = now;
25 }
26
27 return true;
28 }
29
30 int main(void) //2015百度之星初赛1 1003 序列变换
31 {
32 int t, cas = 0;
33 scanf ("%d", &t);
34 while (t--)
35 {
36 scanf ("%d", &n);
37 for (int i=1; i<=n; ++i) scanf ("%d", &a[i]);
38
39 int l = 0, r = 1e6;
40 while (l < r)
41 {
42 int mid = (l + r) >> 1;
43 if (check (mid)) r = mid;
44 else l = mid + 1;
45 }
46
47 printf ("Case #%d:
", ++cas);
48 printf ("%d
", l);
49 }
50
51 return 0;
52 }
53
54 /*
55 2
56 2
57 1 10
58 3
59 2 5 4
60 */