Lydsy2457 双端队列（双端队列思想）

Posted 2020-11-02 lmjer

问题试求至少用几个双端队列可排序

那么我们不妨换过来思考，将数列排好序后，再来找队列个数

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

struct my{
   int x,id;
};

const int maxn=200000+10;
my a[maxn];
int Max[maxn],Min[maxn];

bool cmp(const my &c,const my &d){
     if(c.x==d.x) return c.id<d.id;
     return c.x<d.x;
}

int main(){
    int n;
    scanf("%d",&n);
    for (int i=1;i<=n;i++){
        scanf("%d",&a[i].x);
        a[i].id=i;
    }
    int top=1;
    sort(a+1,a+1+n,cmp);
    Min[1]=a[1].id;
    a[0].id=a[1].id;
    for (int i=1;i<=n;i++){
        if(a[i].x!=a[i-1].x||i==1){
            Max[top]=a[i-1].id;
            Min[++top]=a[i].id;
        }
    }
    int ans=0,h=0x3f3f3f3f;
    bool b=0;
    for (int i=1;i<=top;i++){
        if(!b){
           if(Max[i]<h) h=Min[i];
           else {
            h=Max[i];
            b=1;
           }
        }
        else{
            if(Min[i]>h) h=Max[i];
            else{
                ans++;
                b=0;
                h=Min[i];
            }
        }
    }
    printf("%d\n",ans);
return 0;
}