[Swust OJ 403]--集合删数

 1 #include <iostream>
 2 #include <string>
 3 #include <cstdio>
 4 #include <algorithm>
 5 #include <sstream>//int 转 string
 6 using namespace std;
 7 typedef long long LL;
 8 int main(){
 9     int len, m, front, cnt, end;
10     LL x[60010] = { 0, 1 }, a, b;
11     while (cin >> len >> m){
12         int i = 1, j = 1, k;
13         for (k = 2; k <= len; k++){
14             a = x[i] * 2 + 1;
15             b = x[j] * 4 + 5;
16             if (a > b){
17                 j++;
18                 x[k] = b;
19             }
20             else if (a == b){
21                 i++;
22                 j++;
23                 x[k] = a;
24             }
25             else{
26                 i++;
27                 x[k] = a;
28             }
29         }
30         string s = "", ans = "";
31         for (i = 1; i <= len; i++){
32             stringstream ss;
33             string str;
34             ss << x[i];
35             ss >> str;
36             s += str;
37         }
38         cout << s << endl;
39         string::iterator it = s.begin();
40         s.insert(it, ‘9‘);//有效序列从1开始，防止front越界
41         len = s.size();
42         front = cnt = 0, end = 1;
43         while (end <= len && cnt != m){
44             if (s[end] <= s[front])
45                 s[++front] = s[end++];
46             else{
47                 front--;
48                 cnt++;
49             }
50         }
51         while (end <= len)
52             s[++front] = s[end++];
53         for (i = 1; i < len - m; i++)
54             cout << s[i];
55         cout << endl;
56     }
57     return 0;
58 }