[題目鏈接]

https://www.lydsy.com/JudgeOnline/problem.php?id=4552

[算法]

首先 ， 二分答案x ， 將比x小的數看作1，比x大的數看作0

然後用線段樹檢驗即可

時間復雜度 : O(MlogN^2)

[代碼]

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 10;

int n , m , q;
int a[MAXN],b[MAXN];

struct Que
{
        
 
int op , l , r;
} que[MAXN];
struct Node
{
        int l , r;
        int tag , cnt;
} Tree[MAXN << 2];

template <typename T> inline void chkmax(T &x,T y) { x = max(x,y); }
template <typename T> inline void chkmin(T &x,T y) { x = min(x,y); }
template <typename T> inline void
 
 read(T &x)
{
    T f = 1; x = 0;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) if (c == ‘-‘) f = -f;
    for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - ‘0‘;
    x *= f;
}
inline void update(int index)
{
        Tree[index].cnt = Tree[index << 1].cnt + Tree[index << 1
 
 | 1].cnt;
}
inline void build(int index,int l,int r)
{
        Tree[index].l = l; 
        Tree[index].r = r;
        Tree[index].tag = -1;
        if (l == r)
        {
                Tree[index].cnt = b[l];
                return;
        }
        int mid = (l + r) >> 1;
        build(index << 1,l,mid);
        build(index << 1 | 1,mid + 1,r);
        update(index);
}
inline void pushdown(int index)
{
        int l = Tree[index].l , r = Tree[index].r ,
                mid = (l + r) >> 1;
        if (Tree[index].tag != -1)
        {
                if (Tree[index].tag)
                {
                        Tree[index << 1].cnt = mid - l + 1;
                        Tree[index << 1 | 1].cnt = r - mid;
                        Tree[index << 1].tag = Tree[index << 1 | 1].tag = 1;
                } else
                {
                        Tree[index << 1].cnt = Tree[index << 1 | 1].cnt = 0;
                        Tree[index << 1].tag = Tree[index << 1 | 1].tag = 0;
                }
                Tree[index].tag = -1;
        }
}
inline void modify(int index,int l,int r,int value)
{
        if (l > r) return;
        if (Tree[index].l == l && Tree[index].r == r)
        {
                if (value == 1) Tree[index].cnt = Tree[index].r - Tree[index].l + 1;
                else Tree[index].cnt = 0;
                Tree[index].tag = value;
                return;
        }
        pushdown(index);
        int mid = (Tree[index].l + Tree[index].r) >> 1;
        if (mid >= r) modify(index << 1,l,r,value);
        else if (mid + 1 <= l) modify(index << 1 | 1,l,r,value);
        else 
        {
                modify(index << 1,l,mid,value);
                modify(index << 1 | 1,mid + 1,r,value);
        }
        update(index);
}
inline int query(int index,int l,int r)
{
        if (Tree[index].l == l && Tree[index].r == r) return Tree[index].cnt;
        pushdown(index);
        int mid = (Tree[index].l + Tree[index].r) >> 1;
        if (mid >= r) return query(index << 1,l,r);
        else if (mid + 1 <= l) return query(index << 1 | 1,l,r);
        else return query(index << 1,l,mid) + query(index << 1 | 1,mid + 1,r);
}
inline bool check(int x)
{
        for (int i = 1; i <= n; i++) b[i] = (a[i] <= x);
        build(1,1,n);
        for (int i = 1; i <= m; i++)
        {
                if (que[i].op == 0) 
                {
                        int cnt = query(1,que[i].l,que[i].r);
                        modify(1,que[i].l,que[i].l + cnt - 1,1);
                        modify(1,que[i].l + cnt,que[i].r,0);
                } else
                {
                        int cnt = query(1,que[i].l,que[i].r);
                        modify(1,que[i].l,que[i].r - cnt,0);
                        modify(1,que[i].r - cnt + 1,que[i].r,1);
                }
        }        
        return query(1,q,q) == 1;
}

int main()
{
        
        read(n); read(m);
        for (int i = 1; i <= n; i++) read(a[i]);
        for (int i = 1; i <= m; i++)
        {
                read(que[i].op);
                read(que[i].l);
                read(que[i].r);
        }
        read(q);
        int l = 1 , r = n , ans;
        while (l <= r)
        {
                int mid = (l + r) >> 1;
                if (check(mid))
                {
                        ans = mid;
                        r = mid - 1;
                } else l = mid + 1;
        }
        printf("%d\n",ans);
        
        return 0;
    
}

[TJOI2016&HEOI2016] 排序