hdu1754 I Hate It

http://acm.hdu.edu.cn/showproblem.php?pid=1754

线段树，单点更新

#include <stdio.h>

#define lson l, m, root<<1
#define rson m+1, r, root<<1|1

const int maxn = 200010;
const int minint = 1<<31;
int max1[maxn<<2];

int max(int x, int y)
{
    return x>y? x: y;
}

void push_up(int root)
{
    max1[root] = max(max1[root<<1], max1[root<<1|1]);
}

void build(int l, int r, int root)
{
    int m;
    if(l == r)
    {
        scanf("%d", max1+root);
        return;
    }
    m = (l + r) >> 1;
    build(lson);
    build(rson);
    push_up(root);
}

void update(int x, int change, int l, int r, int root)
{
    int m;
    if(l == r)
    {
        max1[root] = change;
        return;
    }
    m = (l + r) >> 1;
    if(x <= m)
    {
        update(x, change, lson);
    }
    if(m+1 <= x)
    {
        update(x, change, rson);
    }
    push_up(root);
}

int query(int L, int R, int l, int r, int root)
{
    int m, result;
    if(L <= l && r <= R)
    {
        return max1[root];
    }
    result = minint;
    m = (l + r) >> 1;
    if(L <= m)
    {
        result = max(result, query(L, R, lson));
    }
    if(m+1 <= R)
    {
        result = max(result, query(L, R, rson));
    }
    return result;
}

int main()
{
    int n, m, a, b;
    char c;
    while(~scanf("%d%d", &n, &m))
    {
        build(1, n, 1);
        getchar();
        while(m-- && scanf("%c%d%d%*c", &c, &a, &b))
        {
            if(c == 'Q')
            {
                printf("%d\n", query(a, b, 1, n, 1));
                continue;
            }
            update(a, b, 1, n, 1);
        }
    }
    return 0;
}