【SCOI 2007】 降雨量

【题目链接】

点击打开链接

【算法】

线段树

此题细节很多，写程序时要细心！

【代码】

#include<bits/stdc++.h>
using namespace std;
#define MAXN 50010

struct Node
{
        int l,r,mx;
} Tree[MAXN<<];

int i,n,l,r,posl,posr,q,mx;
int sum[MAXN],a[MAXN],y[MAXN];

template <typename T> inline void read(T &x)
{
    int f = ; x = ;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
    for (; isdigit(c); c = getchar()) x = (x << ) + (x << ) + c - '';
    x *= f;
}
template <typename T> inline void write(T x)
{
    if (x < )
    {
        putchar('-');
        x = -x;
    }
    if (x > ) write(x/);
    putchar(x%+'');
}
template <typename T> inline void writeln(T x)
{
    write(x);
    puts("");
}
inline void update(int index)
{
        Tree[index].mx = max(Tree[index<<].mx,Tree[index<<|].mx);
}
inline void build(int index,int l,int r)
{
        int mid;
        Tree[index].l = l; Tree[index].r = r;
        if (l == r)
        {
                Tree[index].mx = a[l];
                return;
        }
        mid = (l + r) >> ;
        build(index<<,l,mid);
        build(index<<|,mid+,r);
        update(index);
}
inline int query_max(int index,int l,int r)
{
        int mid;
        if (Tree[index].l == l && Tree[index].r == r) return Tree[index].mx;
        mid = (Tree[index].l + Tree[index].r) >> ;
        if (mid >= r) return query_max(index<<,l,r);
        else if (mid +  <= l) return query_max(index<<|,l,r);
        else return max(query_max(index<<,l,mid),query_max(index<<|,mid+,r));
}
int main() {

        read(n);
        for (i = ; i <= n; i++)
        {
                read(y[i]);
                read(a[i]);
                if (i == ) sum[i] = ;
                else sum[i] = sum[i-] + (y[i] == y[i-] + );
        }
        build(,,n);
        read(q);
        while (q--)
        {
                read(l); read(r);
                posl = lower_bound(y+,y+n+,l) - y;
                posr = lower_bound(y+,y+n+,r) - y;
                if (r < l)
                {
                        puts("false");
                        continue;
                }
                if (posl == posr)
                {
                        if (l == r) puts("true");
                        else puts("maybe");
                        continue;
                }
                if (posl +  == posr)
                {
                        if (y[posr] == r && y[posl] != l && a[posr] <= a[posl]) puts("false");
                        else if (y[posl] != l || y[posr] != r) puts("maybe");
                        else if (y[posl] != l && y[posr] != r) puts("maybe");
                        else
                        {
                                if (a[posr] > a[posl]) puts("false");
                                else
                                {
                                        if (l +  == r) puts("true");
                                        else puts("maybe");
                                }
                        }
                        continue;
                }
                if (y[posl] == l && y[posr] == r)
                {
                        if (sum[posr] - sum[posl] == r - l)
                        {
                                mx = query_max(,posl+,posr-);
                                if (a[posr] > mx && a[posr] <= a[posl]) puts("true");
                                else puts("false");
                        } else
                        {
                                mx = query_max(,posl+,posr-);
                                if (a[posr] <= mx || a[posr] > a[posl]) puts("false");
                                else puts("maybe");
                        }
                        continue;
                }
                if (y[posl] == l)
                {
                        mx = query_max(,posl+,posr-);
                        if (mx >= a[posl]) puts("false");
                        else puts("maybe");
                        continue;
                }
                if (y[posr] == r)
                {
                        mx = query_max(,posl,posr-);
                        if (mx >= a[posr]) puts("false");
                        else puts("maybe");
                        continue;
                }
                puts("maybe");
        }

        return ;

}