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Icontofig 's Blog // 我们的征程是星辰大海！Away From OI，Come to ICPC（查看友链请点About Me）

2019-08-01 11:29:45 |  1 Comments  |  主席树
```#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <cstdlib>
using namespace std;
int get_num(){
int num = 0;
char c;
bool flag = false;
while((c = getchar()) == ' ' || c == '\r' || c == '\n');
if(c == '-')
flag = true;
else num = c - '0';
while(isdigit(c = getchar()))
num = (num<<3) + (num<<1) + c - '0';
return (flag ? -1 : 1) * num;
}
const int maxn = 2e5+5;
struct tree{
int l,r;
tree *lc,*rc;
int sum;
}pool[maxn<<5],*root[maxn],*null;
int cnt = 0;
void init(){
null = pool;
null->sum = 0;
null->lc = null->rc = null;
null->l = null->r = 0;
return;
}
tree *new_node(){
tree *node = pool + ++cnt;
node->lc = node->rc = null;
node->sum = 0;
node->l = node->r = 0;
return node;
}
tree *build(int l,int r){
tree *node = new_node();
node->l = l;
node->r = r;
if(l == r)return node;
int mid = (l + r) >> 1;
node->lc = ```
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