1 #include <algorithm>
 2 #include <iostream>
 3 #include <cstring>
 4 using namespace std;
 5 
 6 int main()
 7 {
 8     ios::sync_with_stdio(false);
 9     int m;
10     char str[1050];
11     while (cin >> str >> m)
12     {
13         int len = strlen(str);
14         if (len <= m)
15         {
16             cout << "0" << endl;
17             continue;
18         }
19 
20         int flag = 0;
21         int n = len;
22         int l = 0, r = m;
23         for (int i = 0; i < n - m; i++)
24         {
25             char min = str[l];
26             int pos = l;
27             for (int j = l; j <= r; j++)
28             {
29                 if (str[j]< min)
30                 {
31                     min = str[j];
32                     pos = j;
33                 }
34             }
35             l = pos + 1;
36             r++;
37             if (!flag && min == ‘0‘)
38                 continue;
39             cout << min;
40             flag++;
41         }
42 
43         if (!flag)
44             cout << 0;
45         cout << endl;
46     }
47 
48     return 0;
49 }

 1 #include <iostream>
 2 #include <cmath>
 3 #include <string>
 4 
 5 using namespace std;
 6 
 7 string s;
 8 int n;
 9 int st[1050][20];
10 char ans[1050];
11 
12 int Min(int a, int b)
13 {
14     return s[a] <= s[b] ? a : b;
15 }
16 
17 void init()
18 {
19     for (int i = 0; i < s.size(); i++)
20         st[i][0] = i;
21 
22     for (int j = 1; (1 << j) < s.size(); j++)
23         for (int i = 0; i + (1 << j) - 1 < s.size(); i++)
24         {
25             st[i][j] = Min(st[i][j - 1], st[i + (1 << (j - 1))][j - 1]);
26             //cout << i << ends << j << endl;
27         }
28 }
29 
30 int search(int l, int r)
31 {
32     int k = (int)(log((double)(r - l + 1)) / log(2.0));
33     return Min(st[l][k], st[r - (1 << k) + 1][k]);
34 }
35 
36 int main()
37 {
38     ios::sync_with_stdio(false);
39     while (cin >> s >> n)
40     {
41         init();
42         int len = s.size() - n;
43         int pos = 0;
44         int flag = 0;
45         while (len--)
46         {
47             pos = search(pos,n + flag);
48             ans[flag++] = s[pos];
49             //cout << s[pos] << endl;
50             pos++;
51         }
52 
53         flag = 0;
54 
55         for (int i = 0; i < s.size() - n; i++)
56         {
57             if (!flag && ans[i] == ‘0‘)
58                 continue;
59             flag++;
60             cout << ans[i];
61         }
62         if (!flag)
63             cout << 0;
64         cout << endl;
65     }
66 
67     return 0;
68 }