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Cod sursa(job #379986)
#include<stdio.h>
#include<time.h>
#include<stdlib.h>
#define NMAX 3000003
int n,k,i,j,l,r,sol,m[NMAX],*it,*jt;
bool d;
void swap(int &a,int &b) {
int c=a;
a=b;
b=c;
}
int randPiv(int l,int r) {
return l+rand()%(r-l+1);
}
int main() {
freopen("sdo.in","r",stdin);
freopen("sdo.out","w",stdout);
scanf("%d%d",&n,&k);
for(i=1;i<=n;i++) scanf("%d",m+i);
l=1;
r=n;
do {
i=l;
j=r;
it=m+l;
jt=m+r;
swap(m[i],m[randPiv(l,r)]);
d=false;
while(i<j) {
if(*it>*jt) {
swap(*it,*jt);
d=!d;
}
if(d) {
++i;
++it;
}
else {
--j;
--jt;
}
}
if(i==k) sol=*it;
else
if(k<i) r=i-1;
else l=i+1;
} while(!sol);
printf("%d\n",sol);
return 0;
}