A. Reorder the Array (二分变形)

 1 #include <cstdio>
 2 #include <string>
 3 #include <iostream>
 4 #include <algorithm>
 5 #include <cstdbool>
 6 #include <string.h>
 7 #include <math.h>
 8 
 9 
10 using namespace std;
11 
12 const int maxn = 1e5+5;
13 int a[maxn],b[maxn];
14 int vis[maxn]= {0};
15 
16 int binarySearch(int b[],int vis[],int n,int key)
17 {
18     int left = 0,right = n-1;
19     while (left <= right)
20     {
21         int mid = (right + left) / 2;
22         if (b[mid] > key)
23             right = mid - 1;
24         else
25             left = mid + 1;
26     }
27     while (vis[left]!=0 && b[left] > key)
28         left++;
29     if (b[left] <= key)
30         return -1;
31     else{
32         vis[left]++;
33         return left;
34     }
35 }
36 
37 
38 
39 int main()
40 {
41     int n,cnt = 0;
42     cin >> n;
43     for (int i=0;i<n;i++)
44     {
45         cin >> a[i];
46         b[i] = a[i];
47     }
48     sort(b,b+n);
49     for (int i=0;i<n;i++)
50     {
51         int ant = binarySearch(b,vis,n,a[i]);
52         if (ant >= 0)
53             cnt++;
54     }
55     printf("%d\n",cnt);
56     return 0;
57 }