HOJ 2681 Magic-Pen1

来源：互联网发布：成功的网络促销编辑：程序博客网时间：2024/06/07 02:14

N条单位线段一开始全是白色。有操作使得[l,r]变成黑色或者白色，问最后白色的单位线段的个数。
线段树区间修改，lazy。黑色用0表示，白色用1，这样维护一个sum表示白色个数就可以了。

#include <cstdio>#include <algorithm>using namespace std;#define lson l , m , rt << 1#define rson m + 1 , r , rt << 1 | 1const int maxn = 111111;int h , w , n;int col[maxn<<2];int sum[maxn<<2];void PushUp(int rt){    sum[rt] = sum[rt<<1] + sum[rt<<1|1];}void PushDown(int rt,int m){       if (col[rt] == 1)        {              col[rt<<1] = col[rt<<1|1] = col[rt];              sum[rt<<1] = (m - (m >> 1)) * col[rt];              sum[rt<<1|1] = (m >> 1) * col[rt];              col[rt] = 0;       }       else if(col[rt] == -1)       {            col[rt<<1] = col[rt<<1|1] = col[rt];            sum[rt<<1] = 0;            sum[rt<<1|1] = 0;            col[rt] = 0;       }}void build(int l,int r,int rt){       col[rt] = 0;       sum[rt] = 1;       if (l == r) return ;       int m = (l + r) >> 1;       build(lson);       build(rson);       PushUp(rt);}void update(int L,int R,int c,int l,int r,int rt){       if (L <= l && r <= R)        {              col[rt] = c;              if(c == 1)              sum[rt] = c * (r - l + 1);              else sum[rt] = 0;              return ;       }       PushDown(rt , r - l + 1);       int m = (l + r) >> 1;       if (L <= m) update(L , R , c , lson);       if (R > m) update(L , R , c , rson);       PushUp(rt);}int main(){       int  n , m;       while(~scanf("%d%d",&n,&m))        {              build(1 , n , 1);              while (m --)              {                     int a , b , c;                     scanf("%d%d%d",&a,&b,&c);                     if(c == 1)                     update(a , b , -1 , 1 , n , 1);                     else                     update(a , b , 1 , 1 , n , 1);              }              printf("%d\n",sum[1]);       }       return 0;}

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