【题解】
线段树维护区间中1的个数就好了。每次修改就打上标记并把区间的sum改为len-sum.
1 #include<cstdio> 2 #include<algorithm> 3 #include<cstring> 4 #define LL long long 5 #define N 200010 6 #define rg register 7 #define ls (u<<1) 8 #define rs (u<<1|1) 9 #define mid ((a[u].l+a[u].r)>>1) 10 #define len(x) (a[x].r-a[x].l+1) 11 using namespace std; 12 int n,m; 13 struct tree{ 14 int l,r,sum; bool mark; 15 }a[N<<2]; 16 inline int read(){ 17 int k=0,f=1; char c=getchar(); 18 while(c<'0'||c>'9')c=='-'&&(f=-1),c=getchar(); 19 while('0'<=c&&c<='9')k=k*10+c-'0',c=getchar(); 20 return k*f; 21 } 22 void build(int u,int l,int r){ 23 a[u].l=l; a[u].r=r; 24 if(l<r) 25 build(ls,l,mid),build(rs,mid+1,r),a[u].sum=a[ls].sum+a[rs].sum; 26 else{ 27 char c=getchar(); 28 while(c!='0'&&c!='1') c=getchar(); 29 a[u].sum=c-'0'; 30 } 31 } 32 inline void pushdown(int u){ 33 if(!a[u].mark) return; else a[u].mark^=1; 34 a[ls].mark^=1; a[ls].sum=len(ls)-a[ls].sum; 35 a[rs].mark^=1; a[rs].sum=len(rs)-a[rs].sum; 36 } 37 void update(int u,int r,int l){ 38 if(l<=a[u].l&&a[u].r<=r){ 39 a[u].sum=len(u)-a[u].sum; 40 a[u].mark^=1; 41 return; 42 } 43 pushdown(u); 44 if(l<=mid) update(ls,r,l); 45 if(r>mid) update(rs,r,l); 46 a[u].sum=a[ls].sum+a[rs].sum; 47 } 48 int query(int u,int r,int l){ 49 if(l<=a[u].l&&a[u].r<=r) return a[u].sum; 50 pushdown(u); int ret=0; 51 if(l<=mid) ret+=query(ls,r,l); 52 if(r>mid) ret+=query(rs,r,l); 53 return ret; 54 } 55 int main(){ 56 n=read(); m=read(); build(1,1,n); 57 while(m--){ 58 if(read()==1) printf("%d ",query(1,read(),read())); 59 else update(1,read(),read()); 60 } 61 return 0; 62 }