[poj 2104][luogu p3834]Kth Number

Posted 2020-10-09

主席树写一发~

 

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题目大意:

给一个数列,每次询问一个区间内第k小的数.

 

此题主席树(%Fotile96主席)

 

代码如下:

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 using namespace std;
 5 const int N = 200010,M = 12001000;
 6 struct tline{int x,idx;bool operator < (const tline &ano) const{return (x < ano.x) || (x == ano.x && idx < ano.idx);}}a[N];
 7 int getint()
 8 {
 9     int num = 0,s = 1;char ch = getchar();for(;ch < ‘0‘ || ch > ‘9‘;ch = getchar())if(ch == ‘-‘) s = -1;
10     for(;ch >= ‘0‘ && ch <= ‘9‘;ch = getchar()) num = (num << 3) + (num << 1) + ch - ‘0‘;
11     return (s == 1) ? (num) : (-num);
12 }
13 void putint(int x){if(x > 9)putint(x / 10);putchar(x % 10 + ‘0‘);}
14 struct tnode{int lch,rch,sum;}no[M];
15 int m,n,tcnt = 1,rk[N],root[N];
16 void insert(int val,int  &now,int l,int r)
17 {
18     no[tcnt++] = no[now];now = tcnt - 1;no[now].sum++;
19     if(l == r)return;
20     int mid = (l + r) >> 1;
21     if(val <= mid) insert(val,no[now].lch,l,mid);else insert(val,no[now].rch,mid + 1,r);
22 }
23 int query(int L,int R,int x,int l,int r)
24 {
25     if(l == r)return l;
26     int mid = (l + r) >> 1,tmp = no[no[R].lch].sum - no[no[L].lch].sum;
27     if (tmp >= x) return query(no[L].lch,no[R].lch,x,l,mid);
28     else return query(no[L].rch,no[R].rch,x - tmp,mid + 1,r);
29 }
30 int main()
31 {
32     no[0].lch = no[0].rch = no[0].sum = 0;
33     n = getint();m = getint();
34     for(int i = 1;i <= n;i++) {a[i].idx = i;a[i].x = getint();}
35     sort(a + 1,a + n + 1); for(int i = 1;i <= n;i++) rk[a[i].idx] = i;
36     root[0] = 0;
37     for(int i = 1;i <= n;i++) {root[i] = root[i - 1];insert(rk[i],root[i],1,n);}
38     for(int i = 1;i <= m;i++) {int l = getint();int r = getint();int val = getint();putint(a[query(root[l - 1],root[r],val,1,n)].x);putchar(‘\\n‘);}
39     return 0;
40 }

不过话说poj一直wa,似乎是空间的锅...

ps.HDU也有:HDU2665