数据结构——划分树模板

struct node{
int l,r;
int mid(){
return (l + r)>>1;
}
}tt[N<<2];

int toLeft[20]
;
int val[20]
,sorted
;
int n,q;

void build(int l,int r,int rt,int d){
int i;
tt[rt].l = l;
tt[rt].r = r;
if (l == r) return ;
int m = tt[rt].mid();
int lsame = m - l + 1;//先假设做区间与m相等的放满
//一一排除，保证左区间放的是<=sorted[m]的值
for (i = l; i <= r; ++i){
if (val[d][i] < sorted[m]) lsame--;
}

int lpos = l;
int rpos = m + 1;
int same = 0;

for (i = l; i <= r; ++i){
if (i == l) toLeft[d][i] = 0;
else toLeft[d][i] = toLeft[d][i - 1];

if (val[d][i] < sorted[m]){
toLeft[d][i]++;
val[d + 1][lpos++] = val[d][i];
}
else if (val[d][i] > sorted[m]){
val[d + 1][rpos++] = val[d][i];
}
else{
if (same < lsame){
toLeft[d][i]++;
val[d + 1][lpos++] = val[d][i];
same++;
}
else{
val[d + 1][rpos++] = val[d][i];
}
}
}
build(lc,d + 1);
build(rc,d + 1);
}

int query(int L,int R,int k,int d,int rt){
// printf("%d %d\n",L,R);
if (L == R){
return val[d][L];
}
int s = 0;
int ss = 0;
if (L == tt[rt].l){
ss = 0;
s = toLeft[d][R];
}
else{
ss = toLeft[d][L - 1];
s = toLeft[d][R] - toLeft[d][L - 1];
}
if (k <= s){
int newl = tt[rt].l + ss;
int newr = newl + s - 1;
return query(newl,newr,k,d + 1,rt<<1);
}
else{
int m = tt[rt].mid();
int bb = L - tt[rt].l - ss;
int b = R - L + 1 - s;
int newl = m + bb + 1;
int newr = newl + b - 1;
return query(newl,newr,k - s,d + 1,rt<<1|1);
}
}