Hdu1754单点更新

　　和上一题差不多，单点更新，求和，求最值，求乘积之类的，都可以照着搞。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <climits>
#include <string>
#include <iostream>
#include <map>
#include <cstdlib>
#include <list>
#include <set>
#include <queue>
#include <stack>

using namespace std;
#define lson l,mid,rt<<1
#define rson mid+1,r,rt<<1|1
int sum[888888];
void up(int rt)
{
    sum[rt] = max(sum[rt << 1], sum[rt << 1 | 1]);
}
void build(int l, int r, int rt)
{
    if (l == r){
        scanf("%d", &sum[rt]); return;
    }
    int mid = (l + r) >> 1;
    build(lson);
    build(rson);
    up(rt);
}

int ask(int L, int R, int l, int r, int rt)
{
    if (L <= l&&r <= R)return sum[rt];
    int mid = (l + r) >> 1;
    int ans = 0;
    if (L <= mid) ans = max(ans, ask(L, R, lson));
    if (R>mid) ans = max(ans, ask(L, R, rson));
    return ans;
}

void update(int key, int add, int l, int r, int rt)
{
    if (l == r){
        sum[rt] = add; return;
    }
    int mid = (l + r) >> 1;
    if (key <= mid) update(key, add, lson);
    else update(key, add, rson);
    up(rt);
}
int main()
{
    int n, m;
    int a, b;
    char str[100];
    while (scanf("%d%d", &n, &m) != EOF){
        build(1, n, 1);
        for (int i = 0; i<m; i++){
            scanf("%s", str);
            scanf("%d%d", &a, &b);
            if (str[0] == ‘U‘){
                update(a, b, 1, n, 1);
            }
            else printf("%d\n", ask(a, b, 1, n, 1));
        }
    }
    return 0;
}

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