POJ-2528

Problem POJ-2528

https://vjudge.net/problem/POJ-2528

注意到数据范围，因此需要进行离散化。离散化需要注意，在距离大于1的两点需要在中间增加一点。

其他就是普通的线段树。

#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 2e5 + 7;
int n;
int arrL[maxn],arrR[maxn],tot,discreteArr[maxn << 3], ans;
int segmentTree[maxn << 2],lazyMark[maxn << 2];
bool judge[maxn << 3];
void init(){
    memset(judge,false,sizeof judge);
    memset(segmentTree,0,sizeof segmentTree);
    memset(lazyMark,0,sizeof lazyMark);
    memset(discreteArr,0,sizeof discreteArr);
    tot = ans = 0;
}
void pushUp(int rt){

}
void pushDown(int rt){
    if(lazyMark[rt] != 0){
        lazyMark[rt << 1] = lazyMark[rt];
        lazyMark[rt << 1 | 1] = lazyMark[rt];
        segmentTree[rt << 1] = lazyMark[rt];
        segmentTree[rt << 1 | 1] = lazyMark[rt];
        lazyMark[rt] = 0;
    }
}
void modify(int l,int r,int rt,int L,int R, int x){
    if(L <= l && R >= r){
        segmentTree[rt] = x;
        lazyMark[rt] = x;
        return;
    }
    pushDown(rt);
    int mid= (l + r) >> 1;
    if(L <= mid && R >= l) modify(l, mid, rt << 1, L, R, x);
    if(L <= r && R >= mid + 1) modify(mid + 1, r, rt << 1 | 1,L, R, x);
}
int query(int x,int rt,int l,int r){
    if(l == r){
        return segmentTree[rt];
    }
    pushDown(rt);
    int mid = (l + r) >> 1;
    if(x <= mid )   return query(x,rt << 1,l,mid);
    else return query(x,rt << 1 | 1,mid + 1,r);
}
int f(int x){
    int ret = lower_bound(discreteArr,discreteArr + tot,x) - discreteArr + 1;
    return ret;
}
void discretize(){
    for(int i = 0;i < n; ++i){
        discreteArr[tot++] = arrL[i];
        discreteArr[tot++] = arrR[i];
    }
    sort(discreteArr,discreteArr + tot);
    tot = unique(discreteArr, discreteArr + tot) - discreteArr;
    int temp = tot;
    for(int i = 1;i < temp ; ++i){
        if(discreteArr[i] - discreteArr[i-1] > 1){
            discreteArr[tot++] = discreteArr[i-1] + 1;
        }
    }
    sort(discreteArr,discreteArr + tot);
}
int main() {
    int T;
    cin >> T;
    while (T--) {
        init();
        cin >> n;
        for (int i = 0; i < n; ++i) {
            cin >> arrL[i] >> arrR[i];
        }
        discretize();
        for (int i = 0; i < n; ++i) {
//        cout << f(arrL[i]) << ' ' << f(arrR[i]) << endl;
            modify(1, tot, 1, f(arrL[i]), f(arrR[i]), i);
        }
        for (int i = 1; i <= tot; ++i) {
            int temp = query(i, 1, 1, tot);
            if (judge[temp]) continue;
            judge[temp] = true;
            ans++;
        }
        cout << ans << endl;
    }
}