POJ - 3225 - Help with Intervals 【区间的并、交、差、对称差】

#include <cstdio>
#include <iostream>
#define left rt<<1
#define right rt<<1|1
using namespace std;

const int MAXN = (65535 + 5) << 1; // 每一个点都有开、闭两种状态，故乘以2
int XOR[MAXN << 2];
int cover[MAXN << 2];
bool hash[MAXN];

void pushdown(int rt)
{
　　 // cover 优先于 XOR
    if(cover[rt] != -1) {
        cover[left] = cover[right] = cover[rt];
        XOR[left] = XOR[right] = 0;
        cover[rt] = -1;
    }    
    if(XOR[rt]) {
        // 需判断cover没有被赋值的情况
        if(cover[left] != -1) {
            cover[left] ^= 1;
        } else {
            XOR[left] ^= 1;
        }
        
        if(cover[right] != -1) {
            cover[right] ^= 1;
        } else {
            XOR[right] ^= 1;
        }
        XOR[rt] = 0;
    }
}

void update(char type, int ql, int qr, int rt, int l, int r)
{
    if(ql <= l && r <= qr) {
        if(type == ‘U‘) {
            cover[rt] = 1;
            XOR[rt] = 0;
        } else if(type == ‘D‘){
            cover[rt] = 0;
            XOR[rt] = 0;
        } else if(type == ‘C‘ || type == ‘S‘) {
            if(cover[rt] != -1)    cover[rt] ^= 1; // 这里要细心，跟上面的pushdown类似
            else    XOR[rt] ^= 1;
        }
        return;    
    }    
    
    pushdown(rt);
    int m = (l + r) >> 1;
    if(ql <= m)    update(type, ql, qr, left, l, m);
    else {
        if(type == ‘I‘ || type == ‘C‘) {
            cover[left] = 0;
            XOR[left] = 0;
        }
    }
    
    if(qr > m)    update(type, ql, qr, right, m+1, r);
    else {
        if(type == ‘I‘ || type == ‘C‘) {
            cover[right] = 0;
            XOR[right] = 0;
        }
    }
}

void query(int ql, int qr, int rt, int l, int r)
{
    if(cover[rt] != -1) {
        if(cover[rt] == 1) {
            for(int i=l; i<=r; i++) {
                hash[i] = 1;    
            }
        }
        return;
    }
    if(l == r)    return;
    
    pushdown(rt);
    int m = (l + r) >> 1;
    query(ql, qr, left, l, m);
    query(ql, qr, right, m+1, r);
}

int main ()
{
    cover[1] = XOR[1] = 0;
    int a,b;  
    char type, l, r;  
    while(scanf("%c %c%d,%d%c", &type, &l, &a, &b, &r)!=EOF) {  
        a <<= 1;
        b <<= 1;
        if(l == ‘(‘)    a++;
        if(r == ‘)‘)    b--;
        if(a > b) {
            if(type == ‘C‘ || type == ‘I‘) {
                cover[1] = XOR[1] = 0;
            } 
        } else {
            update(type, a, b, 1, 0, MAXN); // O(lgn)
        }
        getchar();
    }  
    
    query(0, MAXN, 1, 0, MAXN); // O(nlgn)
    int s = -1, e, first=1;
    for(int i=0; i<=MAXN; i++) { // O(n)
        if(hash[i] == 1) {
            if(s == -1) {
                s = i;
            }
            e = i;
        } else if(s != -1) {
            if(first)    first = 0;
            else    printf(" ");
            printf("%c%d,%d%c", s&1?‘(‘:‘[‘, s>>1, (e+1)>>1, e&1?‘)‘:‘]‘);
            s = -1;
        }
    }
    if(first)    printf("empty set\n");
    else printf("\n");
    return 0;    
}