线段树(单点更新，区间查询) HDU 1754 I Hate It

题目链接

线段树的模板

 #include<iostream>
 #include<cstdio>
 #include<cmath>
 #include<algorithm>
 #include<cctype>
 #include<cstdlib>
 #include<cstring>

 using namespace std;

 const int Maxn = 2e6 + ;
 int fa[Maxn];
 struct node
 {
     int l, r;
     int value;
     int mid() {
         return (l + r) / ;
     }
 }s[Maxn];
 void build(int i, int l, int r)
 {
     s[i].l = l;
     s[i].r = r;
     s[i].value = ;
     while (r == l) {
         fa[l] = i;
         return;
     }
     build(i * , l, (l + r) / );
     build(i *  + , (l + r) /  + , r);
 }
 void updata(int x)
 {
     if (x == ) return;
     int fi = x / ;
     int a = s[fi * ].value;
     int b = s[fi *  + ].value;
     s[fi].value = max(a, b);
     updata(fi);
 }
 int Max;
 void query(int i, int l, int r)
 {
     if (s[i].l == l && s[i].r == r) {
         Max = max(Max, s[i].value);
         return;
     }
     int m = s[i].mid();
     if (r <= m) query(i << , l, r);
     else if (l > m) query(i <<  | , l, r);
     else {
         query(i << , l, m);
         query(i <<  | , m + , r);
     }

 }
 int main()
 {
     int n, m;
     while (scanf("%d %d", &n, &m) == ) {
         build(, , n);
         for (int i = ;i <= n;i++) {
             int x;
             scanf("%d", &x);
             s[fa[i]].value = x;
             updata(fa[i]);
         }
         while (m--) {
             char t[];
             int a, b;
             scanf("%s", t);
             scanf("%d %d", &a, &b);
             if (t[] == 'Q') {
                 Max = ;
                 query(, a, b);
                 printf("%d\n", Max);
             }
             else {
                 s[fa[a]].value = b;
                 updata(fa[a]);
             }
         }
     }
     return ;
 }