题目链接:
http://codevs.cn/problem/1191/
题意:
题解:
sum表示这段区间白点的个数，初始全部为0。
lazy为1表示到达这个区间需要被更新为白点，到需要更新的时候再pushdown
代码:
1 #include <bits/stdc++.h> 2 using namespace std; 3 typedef long long ll; 4 #define MS(a) memset(a,0,sizeof(a)) 5 #define MP make_pair 6 #define PB push_back 7 const int INF = 0x3f3f3f3f; 8 const ll INFLL = 0x3f3f3f3f3f3f3f3fLL; 9 inline ll read(){ 10 ll x=0,f=1;char ch=getchar(); 11 while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} 12 while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();} 13 return x*f; 14 } 15 ////////////////////////////////////////////////////////////////////////// 16 const int maxn = 4e5+10; 17 18 struct node{ 19 int l,r,sum,lazy; 20 }tree[maxn<<2]; 21 22 void pushup(int rt){ 23 tree[rt].sum = tree[rt<<1].sum + tree[rt<<1|1].sum; 24 } 25 26 void pushdown(int rt,int x){ 27 if(tree[rt].lazy!=-1){ 28 tree[rt<<1].lazy = tree[rt<<1|1].lazy = tree[rt].lazy; 29 tree[rt<<1].sum = (x-(x>>1)); 30 tree[rt<<1|1].sum = (x>>1); 31 tree[rt].lazy = -1; 32 } 33 } 34 35 void build(int rt,int l,int r){ 36 tree[rt].l = l, tree[rt].r = r; 37 tree[rt].lazy = -1; 38 if(l == r) 39 tree[rt].sum = 0; 40 else{ 41 int mid = (l+r)/2; 42 build(rt<<1,l,mid); 43 build(rt<<1|1,mid+1,r); 44 pushup(rt); 45 } 46 } 47 48 void update(int rt,int l,int r){ 49 int L = tree[rt].l, R = tree[rt].r; 50 if(l<=L && R<=r){ 51 tree[rt].lazy = 1; 52 tree[rt].sum = R-L+1; 53 return ; 54 }else{ 55 pushdown(rt,R-L+1); 56 int mid = (L+R)/2; 57 if(l <= mid) update(rt<<1,l,r); 58 if(r > mid) update(rt<<1|1,l,r); 59 pushup(rt); 60 } 61 } 62 63 int main(){ 64 int n=read(),m=read(); 65 build(1,1,n); 66 for(int i=0; i<m; i++){ 67 int a=read(),b=read(); 68 update(1,a,b); 69 cout << n-tree[1].sum << endl; 70 } 71 72 return 0; 73 }