HDU 1754: I Hate It

Posted 2020-10-07

///@author Sycamore
///@date 9/17/2017
///@link http://acm.hdu.edu.cn/showproblem.php?pid=1754
#include<bits/stdc++.h>

using namespace std;
const int MAXN = 200000 + 5;
int val[MAXN];
struct node
{
   int l, r, max_val;
} ST[MAXN << 2];
void Build(int index, int l, int r)
{
   
   ST[index].l = l;
   ST[index].r = r;
   if (l == r) ST[index].max_val = val[l];
   else
   {
      int m = (l + r) >> 1;
      Build(index << 1, l, m);
      Build((index << 1) + 1, m + 1, r);
      ST[index].max_val = max(ST[index << 1].max_val, ST[(index << 1) + 1].max_val);
   }
   
}

void Update(int n, int index, int id)//top-down
{
   if (id < ST[index].l || id > ST[index].r)
      return;
   if (ST[index].l == id && ST[index].r == id)
   {
      ST[index].max_val = n;
      return;
   }
   
   Update(n,index << 1, id);
   Update(n,(index << 1) + 1, id);
   ST[index].max_val = max(ST[index << 1].max_val, ST[(index << 1) + 1].max_val);
}

int Query(int l, int r, int index)//top-down
{
   if (ST[index].l > r || ST[index].r <l)return 0;
   if (ST[index].l >= l && ST[index].r <= r)return ST[index].max_val;
   int m = (ST[index].l + ST[index].r) >> 1;
   if (r <= m)return Query(l, r, index << 1);//in the left interval
   if (l > m)return Query(l, r, (index << 1) + 1);
   return max(Query(l, m, index << 1), Query(m + 1, r, (index << 1) + 1));
}

#define endl ‘\n‘

int main()
{
   ios::sync_with_stdio(false);
   cin.tie(nullptr);
   int n, m;
   while (cin >> n >> m)
   {
      
      
      for (int i = 1; i <= n; i++)cin >> val[i];
      Build(1, 1, n);
      char cmd;
      while (m--)
      {
         cin >> cmd;
         if (cmd == ‘Q‘)
         {
            int l, r;
            cin >> l >> r;
            cout << Query(l, r, 1) << endl;
         }
         else
         {
            int a, id;
            cin >> id >> a;
            Update(a, 1, id);
         }
         
      }
   }
   return 0;
}