hdu 1754 I Hate It

线段树基础题：

 1 #include<stdio.h>

 2 #include<string.h>

 3 #define INF 0x7fffffff

 4 #define MAXN 800000

 5 int N, M, D, tree[MAXN];

 6 

 7 int max(int a, int b)

 8 {

 9     if(a>b) return a;

10     else return b;

11 }

12 

13 void updata(int cur)

14 {

15     for(int i = (D+cur>>1); i^1; i >>= 1)

16         tree[i] = max(tree[i<<1], tree[i<<1|1]);

17 }

18 

19 int query(int x, int y)

20 {

21     int i = D+x-1, j = D+y+1, ans = -INF;

22     for(; i^j^1; i >>= 1, j >>=1)

23     {

24         if(~i&1)

25             ans = max(ans, tree[i^1]);

26         if(j&1)

27             ans = max(ans, tree[j^1]);

28     }

29     return ans;

30 }

31 

32 void init()

33 {

34     while(~scanf("%d%d",&N,&M))

35     {

36         for(D = 1; D < N+2; D <<= 1);

37         memset(tree, 0xc3, sizeof(tree));

38         for(int i = 1; i <= N; i ++)

39             scanf("%d",&tree[D + i]);

40         for(int i = D-1; i > 0; i --)

41             tree[i] = max(tree[i<<1], tree[i<<1|1]);

42         for(int i = 0; i < M; i ++)

43         {

44             char s[5];

45             int a, b;

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

47             if(s[0] == 'Q')

48             {

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

50             }

51             else

52             {

53                 tree[D+a] = b;

54                 updata(a);

55             }

56         }

57     }

58 }

59 

60 int main()

61 {

62     init();

63     return 0;

64 }