hdu1754 I Hate It

题目链接：hdu1754 I Hate It

树状数组学习参考博客：http://blog.csdn.net/u010598215/article/details/48206959

树状数组之前没看懂就放着一直没看了,现在抽空学下...

 #include<cstdio>
 #include<algorithm>
 #include<cmath>
 #include<cstring>
 #define CLR(a,b) memset((a),(b),sizeof((a)))
 using namespace std;
 typedef long long ll;
 const int N = ;
 int n;
 int a[N];
 int tree[N];
 int lowbit(int x){
     return x&(-x);
 }
 void update(int pos){
     int lx, i;
     while(pos <= n){
         tree[pos] = a[pos];
         lx = lowbit(pos);
         for(i = ; i < lx; i <<= )
             tree[pos] = max(tree[pos], tree[pos-i]);
         pos += lowbit(i);
     }
 }
 int query_ma(int x, int y){
     int ma = ;
     while(y >= x){
         ma = max(ma, a[y]);
         y--;
         for(; y - lowbit(y) >= x; y -= lowbit(y))
             ma = max(tree[y], ma);
     }
     return ma;
 }
 int main(){
     int m, i;
     while(~scanf("%d%d", &n, &m)){
         CLR(tree, );
         for(i = ; i <= n; ++i){
             scanf("%d", &a[i]);
             update(i);
         }
         int l, r;
         char c;
         while(m--){
             scanf("%*c%c%d%d", &c, &l, &r);
             if(c == 'Q')
                 printf("%d\n", query_ma(l,r));
             else {
                 a[l] = r;
                 update(l);
             }
         }
     }
     return ;
 }