树状数组求区间最值

http://www.cnblogs.com/ambition/archive/2011/04/06/bit_rmq.html

代码如下：

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<queue>
#include<set>
#include<map>
#include<cstring>
#include<vector>
#include<string>
#define LL long long
#define MAXN 100005
using namespace std;

int N, seq[MAXN], idx[MAXN];

inline int lowbit(int x) {
    return x & (-x);    
}

void modify(int p) {
    for (int i = p; i <= N; ++i) {
        idx[i] = seq[i];
        for (int j = 1; j < lowbit(i); j <<= 1) {
            idx[i] = max(idx[i], idx[i-j]);
        }
    }
}

int query(int L, int R) {
    int ret = seq[R];
    while (1) {
        ret = max(ret, seq[R]);
        if (L == R) break;
        for (R -= 1; R-L >= lowbit(R); R -= lowbit(R)) {
            ret = max(ret, idx[R]);    
        }    
    }
    return ret;
}

int main(  )
{
    int Q, L, R, op, x, y;
    while (scanf("%d", &N) == 1) {
        for (int i = 1; i <= N; ++i) {
            scanf("%d", &seq[i]);
        }
        modify(1);
        scanf("%d", &Q);
        while (Q--) {
            scanf("%d", &op);
            if (op == 1) {
                scanf("%d %d", &L, &R);
                printf("%d\n", query(L, R));
            } else {
                scanf("%d %d", &x, &y);
                seq[x] = y;
                modify(x);
            }
        }
    }
    return 0;
}