【HDU1754】I Hate It（线段树）

update:单点替换 query:区间最值

 #include <iostream>
 #include <cstring>
 #include <cstdlib>
 #include <cstdio>
 #include <numeric>
 #include <cctype>
 #include <algorithm>
 #include <cmath>
 #include <vector>
 #include <climits>
 using namespace std;

 const int maxn = 2e5 + ;
 int maxv[maxn * ];

 void update (int p, int v, int o, int L, int R) {
     int M = L + ((R - L) >> );
     if (L == R) {
         maxv[o] = v;
     } else {
         if (p <= M) {
             update (p, v, o << , L, M);
         } else {
             update (p, v, (o << ) | , M + , R);
         }
         maxv[o] = max (maxv[o * ], maxv[o <<  | ]);
     }
 }

 int query (int ql, int qr, int o, int L, int R) {
     int M = L + (R - L) / , ans = INT_MIN;
     if (ql <= L && R <= qr) {
         return maxv[o];
     }
     if (ql <= M) {
         ans = max (ans, query (ql, qr, o << , L, M));
     }
     if (M < qr) {
         ans = max (ans, query (ql, qr, o <<  | , M + , R));
     }
     return ans;
 }

 int main () {
     int n, ask_n, x, a, b;
     char op[];
     while (~scanf ("%d%d", &n, &ask_n)) {
         memset (maxv, , sizeof(maxv));
         for (int i = ; i <= n; ++ i)  {
             scanf ("%d", &x);
             update (i, x, , , n);
         }

         while (ask_n --) {
             scanf ("%s %d %d", op, &a, &b);

             if (op[] == 'Q') {
                 printf ("%d\n", query (a, b, , , n));
             } else if (op[] == 'U') {
                 update (a, b, , , n);
             }
         }
     }
     return ;
 }