洛谷P1496

P1496 火烧赤壁

初见杀，如何将离散化后的数组标记染色才是最重要的

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#include<bits/stdc++.h>
using namespace std;

vector<int> f(4e4 + 10);
vector<int>d;
vector<int>c;
map<int, int>mp;

int main() {
    int n; cin >> n;
    vector<int>a(n);
    vector<int>b(n);
    long long ans = 0;
    for(int i = 0; i < n; i++) {
        cin >> a[i] >> b[i];
        d.push_back(a[i]);
        d.push_back(b[i]);
    }
    sort(d.begin(), d.end());
    for(int i = 0; i < d.size(); i++) {
        if(d[i] != d[i - 1] || i == 1) {
            c.push_back(d[i]);
            mp[d[i]] = c.size() - 1;
        }
    }
    for(int i = 0; i < d.size(); i++) {
        int x = mp[a[i]], y = mp[b[i]];
        for(int j = x; j < y; j++) f[j] = 1;
    }
    for(int i = 0; i < c.size(); i++) {
        if(f[i]) ans += c[i + 1] - c[i];
    }
    cout << ans << '\n';
    return 0;
}