Codeforces Beta Round #75 (Div. 1 Only) B. Queue 线段树+二分

题目链接:

http://codeforces.com/problemset/problem/91/B

题意:

给你一个数列，让你找到最右边比这个数小的数的位置，如果没有就输出-1

题解:

线段树中二分，查询最小值，然后二分区间就好了

代码:

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 #define MS(a) memset(a,0,sizeof(a))
 5 #define MP make_pair
 6 #define PB push_back
 7 const int INF = 0x3f3f3f3f;
 8 const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;
 9 inline ll read(){
10     ll x=0,f=1;char ch=getchar();
11     while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
12     while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
13     return x*f;
14 }
15 //////////////////////////////////////////////////////////////////////////
16 const int maxn = 1e5+10;
17 
18 int a[maxn],tree[maxn<<2],ans[maxn],cnt;
19 
20 void pushup(int rt){
21     tree[rt] = min(tree[rt<<1],tree[rt<<1|1]);
22 }
23 
24 void build(int rt,int l,int r){
25     tree[rt] = INF;
26     if(l == r){
27         tree[rt] = a[l];
28         return ;
29     }
30 
31     int mid = (l+r)/2;
32     build(rt<<1,l,mid);
33     build(rt<<1|1,mid+1,r);
34     pushup(rt);
35 }
36 
37 void query(int rt,int l,int r,int x){
38     if(l == r){
39         ans[++cnt] = l-x-1;
40         return ;
41     }
42 
43     int mid = (l+r)/2;
44     if(tree[rt<<1|1] < a[x])
45         query(rt<<1|1,mid+1,r,x);
46     else
47         query(rt<<1,l,mid,x);
48 }
49 
50 void update(int rt,int l,int r,int x){
51     if(l == r){
52         tree[rt] = INF;
53         return ;
54     }
55 
56     int mid = (l+r)/2;
57     if(x>mid)
58         update(rt<<1|1,mid+1,r,x);
59     else
60         update(rt<<1,l,mid,x);
61     pushup(rt);
62 }
63 
64 int main(){
65     int n = read();
66     for(int i=1; i<=n; i++)
67         a[i] = read();
68     build(1,1,n);
69 
70     for(int i=1; i<=n; i++){
71         if(tree[1] >= a[i])
72             ans[++cnt] = -1;
73         else
74             query(1,1,n,i);
75         update(1,1,n,i);
76     }
77 
78     for(int i=1; i<=cnt; i++)
79         cout << ans[i] << " ";
80     cout << endl;
81 
82     return 0;
83 }
84 // http://codeforces.com/problemset/problem/91/B