poj-3667（线段树区间合并）

题目链接：传送门

参考文章：传送门

思路：线段树区间合并问题，每次查询到满足线段树的区间最左值，然后更新线段树。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 50500;
int lsum[maxn<<2],rsum[maxn<<2],msum[maxn<<2],cover[maxn<<2];
void build(int x,int l,int r)
{lsum[x]=rsum[x]=msum[x]=r-l+1;if(l==r) return ;int mid=(l+r)>>1;build(x<<1,l,mid);build(x<<1|1,mid+1,r);
}
int MAX(int x,int y)
{return x>y?x:y;
}
void pushup(int x,int k)
{lsum[x]=lsum[x<<1];rsum[x]=rsum[x<<1|1];msum[x]=MAX(MAX(msum[x<<1],msum[x<<1|1]),lsum[x<<1|1]+rsum[x<<1]);if(lsum[x<<1]==(k-(k>>1))) lsum[x]+=lsum[x<<1|1];if(rsum[x<<1|1]==k>>1) rsum[x]+=rsum[x<<1];
}
void pushdown(int x,int k)
{if(cover[x]!=-1){cover[x<<1]=cover[x<<1|1]=cover[x];lsum[x<<1]=rsum[x<<1]=msum[x<<1]=cover[x]?0:(k-(k>>1));lsum[x<<1|1]=rsum[x<<1|1]=msum[x<<1|1]=cover[x]?0:(k>>1);cover[x]=-1;}
}
void update(int x,int l,int r,int A,int B,int Item)
{if(A<=l&&r<=B) {cover[x]=Item;lsum[x]=rsum[x]=msum[x]=Item?0:r-l+1;return ;}pushdown(x,r-l+1);int mid=(l+r)>>1;if(A<=mid) update(x<<1,l,mid,A,B,Item);if(B>mid) update(x<<1|1,mid+1,r,A,B,Item);pushup(x,r-l+1);
}
int query(int x,int l,int r,int len)
{if(l==r) return 1;pushdown(x,r-l+1);int mid=(l+r)>>1;if(msum[x<<1]>=len) return query(x<<1,l,mid,len);else if(rsum[x<<1]+lsum[x<<1|1]>=len) return mid-rsum[x<<1]+1;else return query(x<<1|1,mid+1,r,len);
}
int main(void)
{int n,m,i,x,y,z;while(~scanf("%d%d",&n,&m)){build(1,1,n);while(m--){scanf("%d",&x);if(x==1){scanf("%d",&y);if(msum[1]<y){printf("0\n");continue;}z=query(1,1,n,y);printf("%d\n",z);update(1,1,n,z,z+y-1,1);}else{scanf("%d%d",&y,&z);update(1,1,n,y,y+z-1,0);}}}return 0;
}