4493: Remove Digits
Description
Given an N-digit number, you should remove K digits and make the new integer as large as possible.
Input
The first line has two integers N and K (N不大于500000).
The next line has a N-digit number with no leading zero.
Output
Output the largest possible integers by removing K digits.
Sample Input
4 2
2835
Sample Output
85
在一个字符串里找到n-k位的递减数列or前几位递减，一直超时。。。
贪心用栈实现就好的
#include <stdio.h>
char s[];
int main()
{
int n,k,i,j,f=;
s[]=;
scanf("%d%d",&n,&k);
getchar();
for(i=; i<n; i++)
{
char c;
c=getchar();
while(c>s[f])
{
if(!k||!f)break;
k--;
f--;
}
s[++f]=c;
}
f-=k;
s[++f]=;
printf("%s",s+);
return ;
}