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);
}
}
}