Tunnel Warfare
思路：
没被摧毁的村庄为1，否则为0，用len记录
线段树维护区间的两个信息：
前缀最长1的序列pre
后缀最长1的序列suf
父节点与左右子节点的关系：
//lc为左节点，rc为右节点
1.若左右结点都不满1，则tr[p].pre = tr[lc].pre,tr[p].suf = tr[rc].suf
2.若左节点满1，tr[p].pre = tr[lc].pre + tr[rc].pre;
3.若右节点满1，tr[p].suf = tr[lc].suf + tr[rc].suf;
代码：
#define _CRT_SECURE_NO_WARNINGS 1
#include<algorithm>
#include<fstream>
#include<iostream>
#include<cstdio>
#include<deque>
#include<string>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<vector>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<bitset>
#include<unordered_map>
using namespace std;
#define INF 2e9
#define MAXN 310000
#define N 1000010
#define M 10007
#define endl '\n'
#define exp 1e-8
#define lc p << 1
#define rc p << 1|1
#define lowbit(x) ((x)&-(x))
const double pi = acos(-1.0);
typedef long long LL;
typedef unsigned long long ULL;
inline ULL read() {
ULL x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch>'9') {
if (ch == '-')
f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = (x << 1) + (x << 3) + (ch ^ 48);
ch = getchar();
}
return x * f;
}
void print(ULL x) {
if (x > 9)print(x / 10);
putchar(x % 10 ^ 48);
}
int n, m,idx,his[N];
struct tree
{
int l, r, len, pre, suf;
}tr[N*4];
void pushup(int p)
{
int len = tr[p].r - tr[p].l + 1;
tr[p].pre = tr[lc].pre;
tr[p].suf = tr[rc].suf;
if (len - (len >> 1) == tr[lc].pre) tr[p].pre = tr[lc].pre + tr[rc].pre;
if (len >> 1 == tr[rc].suf) tr[p].suf = tr[lc].suf + tr[rc].suf;
}
void build(int p, int l, int r)
{
tr[p].l = l, tr[p].r = r;
if (l == r)
{
tr[p].len = tr[p].pre = tr[p].suf = 1;
return;
}
int m = l + r >> 1;
build(lc, l, m);
build(rc, m + 1, r);
pushup(p);
}
void update(int p, int x,int c )
{
if (tr[p].l == tr[p].r)
{
tr[p].suf = tr[p].pre = tr[p].len = c;
return;
}
int m = tr[p].l + tr[p].r >> 1;
if (x <= m)update(lc, x, c);
else update(rc, x, c);
pushup(p);
}
int query(int p, int x)
{
if (tr[p].l == tr[p].r)
return tr[p].len;
int m = tr[p].l + tr[p].r >> 1;
if (x <= m)
{
if (x > m - tr[lc].suf)return tr[lc].suf + tr[rc].pre;
else return query(lc, x);
}
else
{
if (x <= m + tr[rc].pre)return tr[lc].suf + tr[rc].pre;
else return query(rc, x);
}
}
int main()
{
while (scanf("%d%d", &n, &m) != EOF)
{
build(1, 1, n);
idx = 0;
while (m--)
{
char a;
int x;
cin >> a;
if (a == 'D')
{
scanf("%d", &x);
his[++idx] = x;
update(1, x, 0);
}
else if (a == 'Q')
{
scanf("%d", &x);
printf("%d\n", query(1, x));
}
else
{
x= his[idx--];
update(1, x, 1);
}
}
}
return 0;
}