I Hate It

I Hate It - HDU 1754 线段树

  国际惯例中文题目不需要解释题意。

  思路：也是个水体，直接裸线段树就可以，没有什么需要注意的地方。写的时候有一个小错误就是刚开始我在本地运行的时候发现Q 1 5一直是零，结果发现是build函数没有写到main里去。

AC代码：

////  main.cpp//  L////  Created by LucienShui on 2017/5/24.//  Copyright © 2017年 LucienShui. All rights reserved.//#include <iostream>#include <algorithm>#include <set>#include <string>#include <vector>#include <queue>#include <map>#include <iomanip>#include <cstdio>#include <cstring>#include <cmath>#include <cctype>#define memset(a,b) memset(a,b,sizeof(a))#define il inline#define ull unsigned long longusing namespace std;const int MAXN=200005;int node[MAXN<<2],a[MAXN];#define ls (u<<1)#define rs (u<<1|1)il void build(int u, int left, int right);il void update(int u, int left, int right, int ai, int num);il int query(int u, int left, int right, int begin, int end);il void read(int n);il void solve(int n, int m);int main (){#ifndef ONLINE_JUDGE    freopen("in.txt","r",stdin);#endif // ONLINE_JUDGE    int n,m;    while(~scanf("%d%d",&n,&m)) {        read(n);        build(1,1,n);        solve(n,m);    }    return 0;}il void build(int u, int left, int right) {    if(left == right) node[u] = a[left];    else {        int mid = (left + right) >> 1;        build(ls, left, mid);        build(rs, mid+1, right);        node[u] = max(node[ls],node[rs]);    }}il void update(int u, int left, int right, int ai, int num) {    if(left == right) {        node[u] = num;        return ;    }    int mid = (left + right) >> 1;    if(ai<=mid) update(ls,left,mid,ai,num);    else update(rs,mid+1,right,ai,num);    node[u] = max(node[ls],node[rs]);}il int query(int u, int left, int right, int begin, int end) {    if(begin <= left && right <= end) return node[u];    int mid = (left + right) >> 1;    if(end <= mid) return query(ls, left, mid, begin, end);    else if(begin > mid) return query(rs, mid+1, right, begin, end);    else return max(query(ls, left, mid, begin, end),query(rs, mid+1, right, begin, end));}il void read(int n) {    for(int i=1 ; i<=n ; i++) scanf("%d",a+i);}il void solve(int n, int m) {    char c;    int a,b;    while(m--) {        scanf(" %c%d%d",&c,&a,&b);        if(c=='Q') printf("%d\n",query(1,1,n,a,b));        else update(1,1,n,a,b);    }}