POJ2528 Mayor's posters

题目链接：http://poj.org/problem?id=2528

线段树比较基础的题目，比较捉急的就是离散化，离散化就是将大的区间映射到小的区间中，具体的看代码吧，这个是傻崽大神的代码，本菜的话决计写不出来这么巧妙的代码，不过不得不说，这次受益匪浅，以后我想我会记住这些东西……

#include <iostream>#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>#include <algorithm>using namespace std;#define lson l, m, rt << 1#define rson m + 1, r, rt << 1 | 1const int maxn = 11111;bool hash[maxn];int li[maxn], ri[maxn];int X[maxn * 3];int col[maxn << 4];int cnt;void PushDown(int rt){    if (col[rt] != -1){        col[rt << 1] = col[rt << 1 | 1] = col[rt];        col[rt] = -1;    }}void update(int ll, int rr, int c, int l, int r, int rt){    if (ll <= l && rr >= r){        col[rt] = c;        return;    }    PushDown(rt);    int m = (l + r) >> 1;    if (ll <= m) update(ll, rr, c, lson);    if (rr > m) update(ll, rr, c, rson);}void query(int l, int r, int rt){    if (col[rt] != -1){        if (!hash[col[rt]]) cnt += 1;        hash[col[rt]] = true;        return;    }    if (l == r) return;    int m = (l + r) >> 1;    query(lson);    query(rson);}int Bin(int key, int n, int X[]){    int l = 0, r = n - 1;    while (l <= r){        int m = (l + r) >> 1;        if (X[m] == key) return m;        if (X[m] < key) l = m + 1;        else r = m - 1;    }}int main(){    int t;    scanf("%d", &t);    while (t--){        int n; scanf("%d", &n);        int nn = 0;        for (int i = 0; i < n; i++){            scanf("%d%d", &li[i], &ri[i]);            X[nn++] = li[i];            X[nn++] = ri[i];        }        sort(X, X + nn);        int m = 1;        for (int i = 1; i < nn; i++){            if (X[i] != X[i - 1]) X[m++] = X[i];        }        sort(X, X + m);        for (int i = m - 1; i > 0; i--){            if (X[i] != X[i - 1] + 1) X[m++] = X[i - 1] + 1;        }        sort(X, X + m);        memset(col, -1, sizeof(col));        for (int i = 0; i < n; i++){            int l = Bin(li[i], m, X);            int r = Bin(ri[i], m, X);            update(l, r, i, 0, m, 1);        }        cnt = 0;        memset(hash, 0, sizeof(hash));        query(0, m, 1);        printf("%d\n", cnt);    }    return 0;}