POJ 2528 Mayor's posters 线段树 区间更新 + 简单哈希函数

区间维护是否被覆盖

贴代码（AC，110ms）

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>#define lson l, m, rt << 1#define rson m + 1, r, rt << 1 | 1using namespace std;const int MAX = 1e5 + 50;bool peo[MAX];int mark[MAX < 2], cnt, h[MAX * 3];int lt[MAX], rt[MAX];void pushDown(int rt){    if(mark[rt] != -1){        mark[rt << 1] = mark[rt << 1 | 1] = mark[rt];        mark[rt] = -1;    }}void update(int qL, int qR, int p, int l, int r, int rt){    if(qL <= l && r <= qR){        mark[rt] = p;        return;    }    pushDown(rt);    int m = (l + r) >> 1;    if(qL <= m)        update(qL, qR, p, lson);    if(m < qR)        update(qL, qR, p, rson);}void query(int l, int r, int rt){    if(mark[rt] != -1){        if(!peo[mark[rt]])            cnt++;        peo[mark[rt]] = true;        return;    }    if(l == r)        return;    int m = (l + r) >> 1;    query(lson);    query(rson);}int hash(int key, int n){    int l = 0, r = n - 1;    while(l <= r){        int m = (l + r) >> 1;        if(key == h[m])            return m;        if(key > h[m])            l = m + 1;        else            r = m - 1;    }    return -1;}int main(){    int ca, n, m, len, a, b;    scanf("%d", &ca);    while(ca--){        memset(mark, -1, sizeof(mark));        memset(peo, false, sizeof(peo));        scanf("%d", &n);        m = 0, len = 1, cnt = 0;        for(int i = 0; i < n; ++i){            scanf("%d%d", lt + i, rt + i);            h[m++] = lt[i], h[m++] = rt[i];        }        sort(h, h + m);        for(int i = 1; i < m; ++i)            if(h[i] != h[i - 1])                h[len++] = h[i];        for(int i = len - 1; i > 0; --i){            if(h[i] != h[i - 1] + 1)                h[len++] = h[i - 1] + 1;        }        sort(h, h + len);        for(int i = 0; i < n; ++i){            a = hash(lt[i], len);            b = hash(rt[i], len);            update(a + 1, b + 1, i, 1, len , 1);        }        query(1, len, 1);        printf("%d\n", cnt);    }    return 0;}