Alphabetic Removals(模拟水题)

You are given a string $s$

if there is at least one letter 'a', remove the leftmost occurrence and stop the algorithm, otherwise go to next item;
if there is at least one letter 'b', remove the leftmost occurrence and stop the algorithm, otherwise go to next item;
...
remove the leftmost occurrence of the letter 'z' and stop the algorithm.

This algorithm removes a single letter from the string. Polycarp performs this algorithm exactly $k$

Help Polycarp find the resulting string.

Input

The first line of input contains two integers $n$

The second line contains the string $s$

Output

Print the string that will be obtained from $s$

If the resulting string is empty, print nothing. It is allowed to print nothing or an empty line (line break).

Examples

Input

15 3
cccaabababaccbc

Output

cccbbabaccbc

Input

15 9
cccaabababaccbc

Output

cccccc

Input

1 1
u

Output

题目意思：给你一个含有n个字符的字符串，删除其中的k个字符，按照字典序列删除，即abcdef......，求出删除完成之后的字符串。

方法一：

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<algorithm>
 4 using namespace std;
 5 struct node
 6 {
 7     int id;///字符在字符串中的位置
 8     int vis;///是否删除的状态
 9     char ch;///字符
10 } s[400010];
11 char x[400010];
12 int my_comp1(node a,node b)///先按照字典序排序升序，字典序相同时按照在字符串位置升序
13 {
14     if(a.ch==b.ch)
15     {
16         return a.id<b.id;
17     }
18     else
19     {
20         return a.ch-'a'<b.ch-'a';
21     }
22 }
23 int my_comp2(node a,node b)///再按照在字符串中的位置升序
24 {
25     return a.id<b.id;
26 }
27 int main()
28 {
29     int n,k,i,len;
30     scanf("%d%d",&n,&k);
31     scanf("%s",x);
32     len=strlen(x);
33     for(i=0; i<len; i++)
34     {
35         s[i].ch=x[i];
36         s[i].id=i;
37         s[i].vis=0;
38     }
39     sort(s,s+len,my_comp1);
40     for(i=0; i<k; i++)
41     {
42         s[i].vis=1;
43     }
44     sort(s,s+len,my_comp2);
45     for(i=0; i<len; i++)
46     {
47         if(s[i].vis==1)
48         {
49             continue;
50         }
51         else
52         {
53             printf("%c",s[i].ch);
54         }
55     }
56     printf("\n");
57     return 0;
58 }

方法二：成批次地按照字典序删除字符，直到删够k个结束，时间复杂度会更低

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<algorithm>
 4 using namespace std;
 5 char s[400010];
 6 char a[]="abcdefghijklmnopqrstuvwxyz";
 7 int main()
 8 {
 9     int n,k;
10     int i,j;
11     char ch;
12     while(scanf("%d%d",&n,&k)!=EOF)
13     {
14        getchar();
15        scanf("%s",s);
16        j=0;
17        ch=a[j];
18        while(1)
19         {
20             for(i=0; i<n; i++)
21             {
22                 if(s[i]==ch)
23                 {
24                    s[i]=' ';
25                    k--;
26                 }
27                 if(k==0)
28                 {
29                     break;
30                 }
31             }
32             ch=a[++j];
33             if(k==0)
34             {
35                 break;
36             }
37         }
38         for(i=0;i<n;i++)
39         {
40             if(s[i]!=' ')
41             {
42                 printf("%c",s[i]);
43             }
44         }
45     }
46     return 0;
47 }

Alphabetic Removals(模拟水题)

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