codevs 1191 树轴染色 线段树区间定值，求和

题目链接:

题意:

题解:

代码:

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define MS(a) memset(a,0,sizeof(a))
#define MP make_pair
#define PB push_back
const int INF = 0x3f3f3f3f;
const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;
inline ll read(){
ll 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*10+ch-'0';ch=getchar();}
return x*f;
}
//////////////////////////////////////////////////////////////////////////
const int maxn = 4e5+10;

struct node{
int l,r,sum,lazy;
}tree[maxn<<2];

void pushup(int rt){
tree[rt].sum = tree[rt<<1].sum + tree[rt<<1|1].sum;
}

void pushdown(int rt,int x){
if(tree[rt].lazy!=-1){
tree[rt<<1].lazy = tree[rt<<1|1].lazy = tree[rt].lazy;
tree[rt<<1].sum = (x-(x>>1));
tree[rt<<1|1].sum = (x>>1);
tree[rt].lazy = -1;
}
}

void build(int rt,int l,int r){
tree[rt].l = l, tree[rt].r = r;
tree[rt].lazy = -1;
if(l == r)
tree[rt].sum = 0;
else{
int mid = (l+r)/2;
build(rt<<1,l,mid);
build(rt<<1|1,mid+1,r);
pushup(rt);
}
}

void update(int rt,int l,int r){
int L = tree[rt].l, R = tree[rt].r;
if(l<=L && R<=r){
tree[rt].lazy = 1;
tree[rt].sum = R-L+1;
return ;
}else{
pushdown(rt,R-L+1);
int mid = (L+R)/2;
if(l <= mid) update(rt<<1,l,r);
if(r > mid) update(rt<<1|1,l,r);
pushup(rt);
}
}

int main(){
int n=read(),m=read();
build(1,1,n);
for(int i=0; i<m; i++){
int a=read(),b=read();
update(1,a,b);
cout << n-tree[1].sum << endl;
}

return 0;
}