HDU 1754 I Hate It

题目链接：https://vjudge.net/problem/HDU-1754
题目大意：

　　略
分析：

　　线段树单点更新模板题，查询最值。
代码如下：

  1 #pragma GCC optimize("Ofast")
  2 #include <bits/stdc++.h>
  3 using namespace std;
  4  
  5 #define INIT() std::ios::sync_with_stdio(false);std::cin.tie(0);
  6 #define Rep(i,n) for (int i = 0; i < (n); ++i)
  7 #define For(i,s,t) for (int i = (s); i <= (t); ++i)
  8 #define rFor(i,t,s) for (int i = (t); i >= (s); --i)
  9 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)
 10 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)
 11 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
 12 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)
 13  
 14 #define pr(x) cout << #x << " = " << x << "  "
 15 #define prln(x) cout << #x << " = " << x << endl
 16  
 17 #define LOWBIT(x) ((x)&(-x))
 18  
 19 #define ALL(x) x.begin(),x.end()
 20 #define INS(x) inserter(x,x.begin())
 21  
 22 #define ms0(a) memset(a,0,sizeof(a))
 23 #define msI(a) memset(a,inf,sizeof(a))
 24 #define msM(a) memset(a,-1,sizeof(a))
 25 
 26 #define MP make_pair
 27 #define PB push_back
 28 #define ft first
 29 #define sd second
 30  
 31 template<typename T1, typename T2>
 32 istream &operator>>(istream &in, pair<T1, T2> &p) {
 33     in >> p.first >> p.second;
 34     return in;
 35 }
 36  
 37 template<typename T>
 38 istream &operator>>(istream &in, vector<T> &v) {
 39     for (auto &x: v)
 40         in >> x;
 41     return in;
 42 }
 43  
 44 template<typename T1, typename T2>
 45 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {
 46     out << "[" << p.first << ", " << p.second << "]" << "
";
 47     return out;
 48 }
 49  
 50 typedef long long LL;
 51 typedef unsigned long long uLL;
 52 typedef pair< double, double > PDD;
 53 typedef pair< int, int > PII;
 54 typedef set< int > SI;
 55 typedef vector< int > VI;
 56 typedef map< int, int > MII;
 57 typedef vector< LL > VL;
 58 typedef vector< VL > VVL;
 59 const double EPS = 1e-10;
 60 const int inf = 1e9 + 9;
 61 const LL mod = 1e9 + 7;
 62 const int maxN = 2e5 + 7;
 63 const LL ONE = 1;
 64 const LL evenBits = 0xaaaaaaaaaaaaaaaa;
 65 const LL oddBits = 0x5555555555555555;
 66 
 67 int n, m; 
 68 int a[maxN];
 69 
 70 #define lson l , mid , rt << 1 
 71 #define rson mid + 1 , r , rt << 1 | 1
 72 
 73 struct SegmentTree{
 74     int st[maxN << 2];
 75     
 76     inline void pushUp(int rt) {
 77         st[rt] = max(st[rt << 1], st[rt << 1 | 1]);
 78     }
 79     
 80     inline void pushDown(int rt) { }
 81     
 82     inline void build(int a[], int l, int r, int rt) {
 83         if(l >= r) {
 84             st[rt] = a[r];
 85             return;
 86         }
 87         int mid = (l + r) >> 1;
 88         build(a, lson);
 89         build(a, rson);
 90         pushUp(rt);
 91     }
 92     
 93     // 单点替换，a[x] = y 
 94     inline void update(int x, LL y, int l, int r, int rt) {
 95         if(l >= r) {
 96             st[rt] = y;
 97             return;
 98         }
 99         int mid = (l + r) >> 1;
100         if(x <= mid) update(x, y, lson);
101         else update(x, y, rson);
102         pushUp(rt);
103     }
104     
105     // 区间查询 
106     inline LL queryMax(int L, int R, int l, int r, int rt) {
107         if(L <= l && r <= R) return st[rt];
108         LL ret = 0;
109         int mid = (l + r) >> 1;
110         
111         if(L <= mid) ret = max(ret, queryMax(L, R, lson));
112         if(R > mid) ret = max(ret, queryMax(L, R, rson));
113         return ret;
114     }
115 };
116 SegmentTree segTr;
117 
118 int main(){
119     INIT();
120     while(cin >> n >> m) {
121         For(i, 1, n) cin >> a[i];
122         segTr.build(a, 1, n, 1);
123         
124         string op;
125         For(i, 1, m) {
126             int x, y;
127             cin >> op >> x >> y;
128             switch(op[0]) {
129                 case 'U' : {
130                     segTr.update(x, y, 1, n, 1);
131                     break;
132                 }
133                 case 'Q' : {
134                     cout << segTr.queryMax(x, y, 1, n, 1) << endl;
135                     break;
136                 }
137             }
138         }
139     }
140     return 0;
141 }
View Code