POJ2182Lost Cows

Lost Cows

Description

N (2 <= N <= 8,000) cows have unique brands in the range 1..N. In a spectacular display of poor judgment, they visited the neighborhood ‘watering hole‘ and drank a few too many beers before dinner. When it was time to line up for their evening meal, they did not line up in the required ascending numerical order of their brands.

Regrettably, FJ does not have a way to sort them. Furthermore, he‘s
not very good at observing problems. Instead of writing down each
cow‘s brand, he determined a rather silly statistic: For each cow in
line, he knows the number of cows that precede that cow in line that do,
in fact, have smaller brands than that cow.

Given this data, tell FJ the exact ordering of the cows.

Input

* Line 1: A single integer, N

* Lines 2..N: These N-1 lines describe the number of cows that
precede a given cow in line and have brands smaller than that cow. Of
course, no cows precede the first cow in line, so she is not listed.
Line 2 of the input describes the number of preceding cows whose brands
are smaller than the cow in slot #2; line 3 describes the number of
preceding cows whose brands are smaller than the cow in slot #3; and so
on.

Output

* Lines
1..N: Each of the N lines of output tells the brand of a cow in line.
Line #1 of the output tells the brand of the first cow in line; line 2
tells the brand of the second cow; and so on.

Sample Input

5
1
2
1
0

Sample Output

2
4
5
3
1

Source

USACO 2003 U S Open Orange

【题解】

从后往前扫，从未确定的数中从小往大数就行了

树状数组 + 二分实现

讲真要不是这个题是树状数组课件里的，我不会往树状数组方向想的

太巧了

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cstdlib>
 5 #include <queue>
 6 #include <vector>
 7 #define max(a, b) ((a) > (b) ? (a) : (b))
 8 #define min(a, b) ((a) < (b) ? (a) : (b)
 9 #define lowbit(x) ((x) & (-1 * (x)))
10
11 inline void read(int &x)
12 {
13     x = 0;char ch = getchar(), c = ch;
14     while(ch < ‘0‘ || ch > ‘9‘)c = ch, ch = getchar();
15     while(ch <= ‘9‘ && ch >= ‘0‘)x = x * 10 + ch - ‘0‘, ch = getchar();
16     if(c == ‘-‘)x = -x;
17 }
18
19 const int MAXN = 10000 + 10;
20
21 int n, num[MAXN], bst[MAXN];
22
23 void modify(int p, int k)
24 {
25     for(;p <= n;p += lowbit(p))bst[p] += k;
26 }
27
28 int ask(int p)
29 {
30     int sum = 0;
31     for(;p;p -= lowbit(p))sum += bst[p];
32     return sum;
33 }
34
35 int erfen(int ans)
36 {
37     int l = 1, r = n, mid;
38     while(l <= r)
39     {
40         mid = (l + r) >> 1;
41         if(ask(mid) < ans)l = mid + 1;
42         else r = mid - 1;
43     }
44     return l;
45 }
46
47 int main()
48 {
49     read(n);
50     for(register int i = 2;i <= n;++ i) read(num[i]);
51     for(register int i = 1;i <= n;++ i) modify(i, 1);
52     for(register int i = n;i >= 1;-- i)
53     {
54         num[i] = erfen(num[i] + 1);
55         modify(num[i], -1);
56     }
57     for(register int i = 1;i <= n;++ i) printf("%d\n", num[i]);
58     return 0;
59 }

POJ2182