算法题-数组的最长非递减子序列

 1 int binSearch(const vector<int> &tail, int len, int key)//
 2 {
 3     int left = 0, right = len - 1;
 4     int mid;
 5 
 6     while(left <= right)
 7     {
 8         mid = left + ((right - left) >> 1);
 9         if(tail[mid] == key)
10             return mid;
11         else if(tail[mid] > key)
12             right = mid - 1;
13         else
14             left = mid + 1;
15     }
16 
17     return left;//
18 }
19 
20 void LIS(int *a, int n)
21 {
22     vector<int> tail(n); //当前子序列的结尾，递增的
23     vector<int> orig(n); //当前结尾在原始数组的下标
24     vector<int> prev(n); //当前结尾的上一元素下标
25     int len = 0;
26 
27     tail[0] = a[0];//
28     orig[0] = 0;
29     prev[0] = -1;
30     ++len;
31 
32     for(int i = 1; i < n; ++i)
33     {
34         if(a[i] > tail[len - 1])//
35         {
36             tail[len] = a[i];//
37             orig[len] = i;
38             prev[i]   = orig[len - 1];
39                         
40             ++len;
41         }
42         else
43         {
44             int pos = binSearch(tail, len, a[i]);
45             tail[pos] = a[i];//
46             orig[pos] = i;
47             prev[i]   = pos > 0 ? orig[pos - 1] : -1;
48         }
49     }
50 
51     stack<int> stk;//
52     for(int cur = orig[len - 1]; cur >= 0; cur = prev[cur])
53     {
54         stk.push(a[cur]);
55     }
56 
57     cout << len << endl;
58     while(!stk.empty())
59     {
60         cout << stk.top() << ‘ ‘;
61         stk.pop();
62     }
63     cout << endl;
64 }