HDU 1754 I Hate It(线段树-水题,模板题)

#include <iostream>
#include <cstdio>
#include <fstream>
#include <algorithm>
#include <cmath>
#include <deque>
#include <vector>
#include <queue>
#include <string>
#include <cstring>
#include <map>
#include <stack>
#include <set>
#include <list>
#define INF 0x3f3f3f
#define maxn 200000 + 50
#define juzheng 300

#define ll long long

using namespace std;

//Date:2017-9-4
//Author：HarryBlackCat

struct xx{
int left;
int right;
int val;
}tree[maxn + maxn + maxn + maxn];

int arr[maxn],n,ans,m;

void bulid_tree(int node,int left,int right){
tree[node].left = left;
tree[node].right = right;

if(left == right)
tree[node].val = arr[left];
else{
int mid = (left + right) / 2;
bulid_tree(node * 2,left,mid);
bulid_tree(node * 2 + 1,mid + 1,right);

tree[node].val = max(tree[node * 2].val,tree[node * 2 + 1].val);
}
}

void add(int node,int index,int val){
tree[node].val = max(tree[node].val,val);

if(tree[node].right == tree[node].left)
return;

int mid = (tree[node].left + tree[node].right) / 2;
if(index > mid)
add(node * 2 + 1,index,val);
else
add(node * 2,index,val);
}

void get_max(int node,int left,int right){
if(tree[node].left >= left && tree[node].right <= right)
ans = max(ans,tree[node].val);
else{
int mid = (tree[node].left + tree[node].right) / 2;
if(left > mid)
get_max(node * 2 + 1,left,right);
else if(right <= mid)
get_max(node * 2,left,right);
else{
get_max(node * 2,left,right);
get_max(node * 2 + 1,left,right);
}
}
}

int main() {
char c;
int a,b;
while(~scanf("%d %d",&n,&m)) {
for(int i = 1; i <= n; i++)
scanf("%d",&arr[i]);

bulid_tree(1,1,n);

while(m--) {
cin >> c;
scanf("%d %d",&a,&b);
if(c == 'Q'){
ans = -INF;
get_max(1,a,b);
printf("%d\n",ans);
}
else
add(1,a,b);
}
}
return 0;
}