【HDU1754】I Hate It（线段树）

update:单点替换 query:区间最值

 

 

 1 #include <iostream>

 2 #include <cstring>

 3 #include <cstdlib>

 4 #include <cstdio>

 5 #include <numeric>

 6 #include <cctype>

 7 #include <algorithm>

 8 #include <cmath>

 9 #include <vector>

10 #include <climits>

11 using namespace std;

12 

13 const int maxn = 2e5 + 10;

14 int maxv[maxn * 3];

15 

16 void update (int p, int v, int o, int L, int R) {

17     int M = L + ((R - L) >> 1);

18     if (L == R) {

19         maxv[o] = v;

20     } else {

21         if (p <= M) {

22             update (p, v, o << 1, L, M);

23         } else {

24             update (p, v, (o << 1) | 1, M + 1, R);

25         }

26         maxv[o] = max (maxv[o * 2], maxv[o << 1 | 1]);

27     }

28 }

29 

30 int query (int ql, int qr, int o, int L, int R) {

31     int M = L + (R - L) / 2, ans = INT_MIN;

32     if (ql <= L && R <= qr) {

33         return maxv[o];

34     }

35     if (ql <= M) {

36         ans = max (ans, query (ql, qr, o << 1, L, M));

37     }

38     if (M < qr) {

39         ans = max (ans, query (ql, qr, o << 1 | 1, M + 1, R));

40     }

41     return ans;

42 }

43 

44 int main () {

45     int n, ask_n, x, a, b;

46     char op[5];

47     while (~scanf ("%d%d", &n, &ask_n)) {

48         memset (maxv, 0, sizeof(maxv));

49         for (int i = 1; i <= n; ++ i)  {

50             scanf ("%d", &x);

51             update (i, x, 1, 1, n);

52         }

53 

54         while (ask_n --) {

55             scanf ("%s %d %d", op, &a, &b);

56 

57             if (op[0] == 'Q') {

58                 printf ("%d\n", query (a, b, 1, 1, n));

59             } else if (op[0] == 'U') {

60                 update (a, b, 1, 1, n);

61             }

62         }

63     }

64     return 0;

65 }