HDU 1754 I Hate It

线段树单点更新和求最大值

#include <stdio.h>
#define lson l, m, rt<<1
#define rson m + 1, r, rt<<1|1
const int maxn = 200005;
int MAX[maxn<<2];
int max(int a, int b) {return a>b?a:b;}
void pushUp(int rt){
    MAX[rt] = max(MAX[rt<<1], MAX[rt<<1|1]);
}
void build(int l, int r, int rt){
    if(l == r){
        scanf("%d", &MAX[rt]);
        return;
    }
    int m = (l + r) >> 1;
    build(lson);
    build(rson);
    pushUp(rt);
}
void update(int p, int sc, int l, int r, int rt)
{
    if(l == r){
        MAX[rt] = sc;
        return;
    }
    int m = (l + r) >> 1;
    if(p <= m) update(p, sc, lson);
    else update(p, sc, rson);
    pushUp(rt);
}
int query(int L, int R, int l, int r, int rt){
    if(L <= l&&r <= R){
        return MAX[rt];
    }
    int m = (l + r) >> 1;
    int ret = 0;
    if(L <= m) ret = max(ret, query(L, R, lson));
    if(R > m) ret = max(ret, query(L, R, rson));
    return ret;
}
int main()
{
    int n, m, a, b;
    char op[3];
    while(scanf("%d %d", &n, &m) != EOF){
        build(1, n, 1);
        while(m--){
            scanf("%s%d%d", op, &a, &b);
            if(op[0] == 'Q') printf("%d\n", query(a, b, 1, n, 1));
            else update(a, b, 1, n, 1);
        }
    }
}