PKU 2777 【线段树】

统计的时候关键是看完全被覆盖的线段是否和目标线段有交，如果有交，则把标记数组中相应的颜色设为true,扫描一下标记数组就可以得到颜色个数。

#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;
const int MAXN = 100010;
int cnt;
bool flag = false;
bool ans[100];
int stNum;
struct node
{
    int l;
    int r;
    int mid;
    int c;
};
node seg_tree[MAXN*4];
void make(int num,int l,int r)
{
    seg_tree[num].l = l;
    seg_tree[num].r = r;
    seg_tree[num].mid = (l+r)/2;
    seg_tree[num].c = 1;
    if (l+1!=r)
    {
        make(num*2,l,seg_tree[num].mid);
        make(num*2+1,seg_tree[num].mid,r);
    }
}
void insert(int num,int a,int b,int c)
{
    if (seg_tree[num].c!=c)
    {
        if (seg_tree[num].l==a&&seg_tree[num].r==b)
        {
            seg_tree[num].c = c;
            return;
        }
        if (seg_tree[num].c>=1)
        {
            seg_tree[2*num].c = seg_tree[num].c;
            seg_tree[2*num+1].c = seg_tree[num].c;
            seg_tree[num].c = -1;
        }

        if (b<=seg_tree[num].mid)
        {
            insert(2*num,a,b,c);
        }
        else if (a>=seg_tree[num].mid)
        {
            insert(2*num+1,a,b,c);
        }
        else
        {
            insert(2*num,a,seg_tree[num].mid,c);
            insert(2*num+1,seg_tree[num].mid,b,c);
        }
    }
}
void cal(int num,int l,int r)
{
    if(seg_tree[num].c>=1)
    {
        if(!(r<=seg_tree[num].l||l>=seg_tree[num].r))//关键：判断是否和目标线段相交
        {
            ans[seg_tree[num].c] = true;
        }
        return;
    }
    if(seg_tree[num].l+1!=seg_tree[num].r)
    {
        cal(2*num,l,r);
        cal(2*num+1,l,r);
    }
}
int main()
{

    int l,t,o;
    int a,b,c;
    char op[4];
    scanf("%d%d%d",&l,&t,&o);
          make(1,1,l+1);
    for (int i=0;i<o;i++)
    {
        scanf("%s",op);
        if (op[0]=='C')
        {
            scanf("%d%d%d",&a,&b,&c);
            if (a>b)
            {
                swap(a,b);
            }
            b++;
            insert(1,a,b,c);
        }
        else
        {

            scanf("%d%d",&a,&b);
            if (a>b)
            {
                swap(a,b);
            }
            b++;

            flag = false;
            memset(ans,false,sizeof(ans));
            cal(1,a,b);
            int res = 0;
            for (int j=1;j<=t;j++)
            {
                if (ans[j])
                {
                    res++;
                }
            }
            printf("%d\n",res);
        }
    }
    return 0;
}