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;

}