HDU 6047 Maximum Sequence

贪心的思路是很好找到的,本题命门不在桶排序,其实直接sort也可以,而在如何得到区间最大值上.
我看到网上有人用线段树维护最大值,但这样其实慢了.
此处应该是用单调队列,所谓单调队列,网上一篇博客写的很好,就像是
“移窗子”,很好的维护这种情况的最值.
具体看代码

/*  xzppp  */#include <iostream>#include <vector>#include <set>#include <queue>#include <map>#include <algorithm>#include <stdio.h>#include <string.h>#include <list>using namespace std;#define FFF freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);const int MAXN = 250000;const int INF = 0x7ffffff;const int MOD = 1e9+7;typedef long long  LL;int a[MAXN*2+17],c[MAXN*2+17],t[MAXN+17];int main(){    //FFF    int n;    while(scanf("%d",&n)==1){        memset(t, 0, sizeof(t));        for (int i = 0; i < n; ++i){            scanf("%d",&a[i]);            a[i]-=(i+1);        }        for (int i = 0; i < n; ++i){               int temp;            scanf("%d",&temp);            t[temp]++;        }        int head=0,rear=0;        for(int i=0;i<n;++i)   {            while(rear>head&&a[c[rear-1]]<a[i]) rear--;            c[rear++] = i;        }        int temp=1;        for(int i=n;i<2*n;++i)   {            while(!t[temp]) temp++;            t[temp]--;            while(c[head]<temp-1) head++;            a[i] = a[c[head]]-i-1;            while(rear>head&&a[c[rear-1]]<a[i]) rear--;              c[rear++] = i;          }        LL ans = 0;        for (int i = n; i < 2*n; ++i)            ans = (ans+a[i]+(i+1))%MOD;        printf("%d\n",ans );    }    return 0;}