hdu1754 I Hate It--更新查询最大值

原题链接： ​​http://acm.hdu.edu.cn/showproblem.php?pid=1754​​

一：分析

模板题，没什么难的，直接看代码就行。

二：AC代码

#define _CRT_SECURE_NO_DEPRECATE 

#include<iostream>
#include<algorithm>
using namespace std;

struct Node
{
  int left;
  int right;
  int mid;
  int maxx;
};

Node node[1<<20];//2^20稍微大200,000

void build(int left, int right, int pos)
{
  node[pos].left = left;
  node[pos].right = right;
  node[pos].mid = (left + right) / 2 + 1;
  node[pos].maxx = 0;

  if (left == right)
    return;

  build(left, (left + right) / 2, 2 * pos);
  build((left + right) / 2 + 1, right, 2 * pos + 1);
}

void update(int k, int value, int pos)
{
  node[pos].maxx = max(node[pos].maxx, value);

  if (node[pos].left == k&&node[pos].right == k)
    return;

  if (k < node[pos].mid)
    update(k, value, 2 * pos);
  else
    update(k, value, 2 * pos + 1);
}

int query(int left, int right, int pos)
{
  if (node[pos].left == left&&node[pos].right == right)
    return node[pos].maxx;

  if (left < node[pos].mid)
  {
    if (right < node[pos].mid)
      return query(left, right, 2 * pos);
    else
      return max(query(left, node[pos].mid - 1, 2 * pos), query(node[pos].mid, right, 2 * pos + 1));
  }
  else
    return query(left, right, 2 * pos + 1);
}

int main()
{
  int n, m;
  int x;
  char ch[2];
  int a, b;

  while (~scanf("%d%d", &n, &m))
  {
    build(1, n, 1);

    for (int i = 1; i <= n; i++)
    {
      scanf("%d", &x);
      update(i, x, 1);
    }

    for (int i = 1; i <= m; i++)
    {
      scanf("%s%d%d", ch, &a, &b);

      if (ch[0] == 'Q')
        printf("%d\n", query(a, b, 1));
      else
        update(a, b, 1);
    }
  }
  return 0;
}