POJ 3667 Hotel 线段树 区间合并 入门题

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
#define maxn 50003
#define lson l, m, rt<<1
#define rson m+1, r, rt<<1|1
#define mid int m = (l + r)>>1
int col[maxn<<2];
int lsum[maxn<<2], msum[maxn<<2], rsum[maxn<<2];
int n, m;
int max(int a , int b) { return a > b ? a : b; }

void pushup(int rt, int len)
{
lsum[rt] = lsum[rt<<1];
rsum[rt] = rsum[rt<<1|1];
if(lsum[rt] == len - (len>>1)) lsum[rt] += lsum[rt<<1|1];
if(rsum[rt] == (len>>1)) rsum[rt] += rsum[rt<<1];
msum[rt] = max(rsum[rt<<1] + lsum[rt<<1|1],  max(msum[rt<<1], msum[rt<<1|1]) );
}

void pushdown(int rt, int len)
{
if(col[rt] != -1)
{
col[rt<<1] = col[rt<<1|1] = col[rt];
lsum[rt<<1] = rsum[rt<<1] = msum[rt<<1] = col[rt] ? 0 :(len - (len >>1));
lsum[rt<<1|1] = rsum[rt<<1|1] = msum[rt<<1|1] = col[rt] ? 0 : (len>>1) ;
col[rt] = -1;
}
}

void build(int l, int r, int rt)
{
lsum[rt] = msum[rt] = rsum[rt] = r-l+1;
col[rt] = -1;
if(l == r)
return;
mid;
build(lson);
build(rson);
}

void update(int L, int R, int v, int l, int r, int rt)
{
if(L <= l && r <= R )
{
col[rt] = v;
lsum[rt] = msum[rt] = rsum[rt] = v ? 0 : (r-l+1);
return;
}
pushdown(rt, r-l+1);
mid;
if(L <= m) update(L, R, v, lson);
if(R > m) update(L, R, v, rson);
pushup(rt, r-l+1);
}
int query(int v, int l, int r, int rt)
{
if(l == r) return l;
pushdown(rt, r-l+1);
mid;
if(msum[rt<<1] >= v) return query(v, lson);
else if( rsum[rt<<1] + lsum[rt<<1|1] >= v)
return m - rsum[rt<<1] + 1;
else
return query(v, rson);
}
int main()
{
int i, j;
while( ~scanf("%d%d", &n, &m))
{
int op, x, y;
build(1, n, 1);
while(m--)
{
scanf("%d%d", &op, &x);
if(op == 1)
{
if(msum[1] < x)
puts("0");
else
{
int k = query(x, 1, n, 1);
printf("%d\n", k);
update(k , k+x-1, 1, 1, n, 1);
}
}
else
{
scanf("%d", &y);
update(x, x+y-1, 0, 1, n, 1);
}
}
}
return 0;
}