hdu 4417 Super Mario 划分树+二分

http://acm.hdu.edu.cn/showproblem.php?pid=4417

题意：

给定一个长度为n的序列，求区间[L,R]中小于h的个数；

思路：

分三种情况：

1：如果该区间最小值都大于h输出0；

2：如果该区间最大值小于等于h输出区间长度：

3：否则，二分枚举该区间的第m大，直到找到第m大为最后一个小于等于h的；

View Code

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <string>

#define CL(a,num) memset((a),(num),sizeof(a))
#define iabs(x)  ((x) > 0 ? (x) : -(x))
#define Min(a , b) ((a) < (b) ? (a) : (b))
#define Max(a , b) ((a) > (b) ? (a) : (b))

#define ll __int64
#define inf 0x7f7f7f7f
#define MOD 100000007
#define lc l,m,rt<<1
#define rc m + 1,r,rt<<1|1
#define pi acos(-1.0)
#define test puts("<------------------->")
#define maxn 100007
#define M 100007
#define N 100007
using namespace std;
//freopen("din.txt","r",stdin);
struct node{
int l,r;
int mid(){
return (l + r)>>1;
}
}tt[N<<2];

int toLeft[20]
,val[20]
;
int sorted
;
int n,m;
int MIN,MAX;

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;
for (i = l; i <= r; ++i){
if (val[d][i] < sorted[m]) lsame--;
}

int lpos = l,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){
same++;
val[d + 1][lpos++] = val[d][i];
toLeft[d][i]++;
}
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){
if (L == R) return val[d][L];
int s,ss;
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 (s >= k){
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);
}
}
int bSearch(int l,int r,int h,int x,int y){
int ans = 0;
while (l <= r){
int m = (l + r)>>1;
if (query(x,y,m,0,1) > h)
r = m - 1;
else{
l = m + 1;
ans = m;
}
}
return ans;
}
int Input(){
char ch = getchar();
while (ch < '0' || ch > '9') ch = getchar();
int num = 0;
while (ch >= '0' && ch <= '9'){
num = num*10 + ch - '0';
ch = getchar();
}
return num;
}
int main(){
//freopen("din.txt","r",stdin);
int t,i;
int x,y,h;
int cas = 1;
t = Input();
while (t--){
printf("Case %d:\n",cas++);
n = Input();
m = Input();
for (i = 1; i <= n; ++i){
val[0][i] = Input();
sorted[i] = val[0][i];
}
sort(sorted + 1,sorted + 1 + n);
build(1,n,1,0);
while (m--){
x = Input();
y = Input();
h = Input();
x++; y++;
MIN = 1;
MAX = y - x + 1;
if (query(x,y,MIN,0,1) > h) puts("0");
else if (query(x,y,MAX,0,1) <= h) printf("%d\n",MAX);
else{
int pos = bSearch(MIN,MAX,h,x,y);
printf("%d\n",pos);
}
}
}
return 0;
}