hdu 1754 I Hate It

线段树基础题：

#include<stdio.h>
#include<string.h>
#define INF 0x7fffffff
#define MAXN 800000
int N, M, D, tree[MAXN];

int max(int a, int b)
{
    if(a>b) return a;
    else return b;
}

void updata(int cur)
{
    for(int i = (D+cur>>1); i^1; i >>= 1)
        tree[i] = max(tree[i<<1], tree[i<<1|1]);
}

int query(int x, int y)
{
    int i = D+x-1, j = D+y+1, ans = -INF;
    for(; i^j^1; i >>= 1, j >>=1)
    {
        if(~i&1)
            ans = max(ans, tree[i^1]);
        if(j&1)
            ans = max(ans, tree[j^1]);
    }
    return ans;
}

void init()
{
    while(~scanf("%d%d",&N,&M))
    {
        for(D = 1; D < N+2; D <<= 1);
        memset(tree, 0xc3, sizeof(tree));
        for(int i = 1; i <= N; i ++)
            scanf("%d",&tree[D + i]);
        for(int i = D-1; i > 0; i --)
            tree[i] = max(tree[i<<1], tree[i<<1|1]);
        for(int i = 0; i < M; i ++)
        {
            char s[5];
            int a, b;
            scanf("%s%d%d",s,&a,&b);
            if(s[0] == 'Q')
            {
                printf("%d\n",query(a,b));
            }
            else
            {
                tree[D+a] = b;
                updata(a);
            }
        }
    }
}

int main()
{
    init();
    return 0;
}