这是一道经典题目,不过易错点就是最后注意如果要选最后一个点的话,那么他前一个点就一定不会选了。
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
typedef long long ll;
struct node
{
int f, n, v,num;
};
bool operator<(const node &a, const node &b)
{
return a.v > b.v;
}
priority_queue<node, vector<node> >que;
node nod[200010];
int n, k;
bool isclear[200010];
int alltot;
int main()
{
scanf("%d%d", &n, &k);
int now, last;
alltot = 1;
scanf("%d", &last);
for (int i = 1; i <= n-1; i++)
{
scanf("%d", &now);
nod[alltot].v = now - last;
nod[alltot].f = alltot - 1;
nod[alltot].n = alltot + 1;
nod[alltot].num = alltot;
last = now;
alltot++;
}
alltot--;
nod[alltot].n = 0;
for (int i = 1; i <= alltot; i++)
que.push(nod[i]);
ll ans = 0;
while (k)
{
node kk;
do{
kk= que.top();
que.pop();
} while (isclear[kk.num]);
ans += kk.v;
int f = nod[kk.num].f; int n = nod[kk.num].n;
int gf = nod[f].f; int gn = nod[n].n;
isclear[kk.num] = 1; isclear[f] = 1; isclear[n] = 1;
if (n == 0)
{
nod[gf].n = 0;
k--;
continue;
}
if (f == 0)
{
nod[gn].f = 0;
k--;
continue;
}
alltot++;
nod[alltot].v = nod[f].v + nod[n].v - kk.v; nod[alltot].num = alltot;
nod[alltot].f = gf; nod[gf].n = alltot;
nod[alltot].n = gn; nod[gn].f = alltot;
que.push(nod[alltot]);
k--;
}
printf("%lld\n", ans);
return 0;
}