UVA - 12532 Interval Product

线段树。因为只需知道正负，所以把正数改成1，负数改成-1就行了。

//基于RMQ的线段树

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
const int Max_N = 1000010;//因为数组开小了RE了很久，闷闷地改成了10^6，就A了
int n, dat[2 * Max_N - 1], m;
int N;
void init(int n_)
{
n = 1;
while (n < n_)n *= 2;
for (int i = 0; i < 2 * n - 1; i++)dat[i] = 1;
}
void update(int k, int a)
{
k += n - 1;
dat[k] = a;
while (k>0)
{
k = (k - 1) / 2;
dat[k] = dat[k * 2 + 1] * dat[k * 2 + 2];
}
}
int query(int a, int b, int k, int l, int r)//求[a,b)乘积正负
{
if (r <= a || b <= l)return 1;
if (a <= l && r <= b)return dat[k];
else
{
int vl = query(a, b, k * 2 + 1, l, (l + r) / 2);
int vr = query(a, b, k * 2 + 2, (l + r) / 2, r);
return vl*vr;
}
}
int main()
{
int a, b;
char order;
while (cin >> N >> m)
{
init(N);
for (int i = 0; i < N; i++)
{
cin >> a;
if (a>0)a = 1;
else if (a < 0)a = -1;
update(i, a);
}
while (m--)
{
cin >> order >> a >> b;
a--;
if (order == 'P')
{
int ans = query(a, b, 0, 0, n);
if (ans>0)printf("+");
else if (ans == 0)printf("0");
else printf("-");
}
else if (order == 'C')
{
if (b>0)b = 1;
else if (b < 0)b = -1;
update(a, b);
}
}
printf("\n");
}
}