Submission #65018031

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#ifndef _Alignof
#define _Alignof __alignof__
#endif
#include <bits/stdc++.h>
#include <numeric>
#define LOOP(n) for (int _i = 0; _i < (n); _i++)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RREP(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, r, n) for (int i = (r); i < (n); ++i)
#define ALL(obj) begin(obj), end(obj)
#define yes "Yes"
#define no "No"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<ll,int> pli;
typedef pair<int,ll> pil;
typedef vector<vector<int>> vvi;
typedef vector<vector<ll>> vvl;
const vector<char> alpha = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
 
 
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#ifndef _Alignof
#define _Alignof __alignof__
#endif
#include <bits/stdc++.h>
#include <numeric>
#define LOOP(n) for (int _i = 0; _i < (n); _i++)
#define REP(i, n) for (int i = 0; i < (n); ++i)
#define RREP(i, n) for (int i = (n); i >= 0; --i)
#define FOR(i, r, n) for (int i = (r); i < (n); ++i)
#define ALL(obj) begin(obj), end(obj)
#define yes "Yes"
#define no "No"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<ll,int> pli;
typedef pair<int,ll> pil;
typedef vector<vector<int>> vvi;
typedef vector<vector<ll>> vvl;
const vector<char> alpha = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
int dx[4] = {0, 1, 0, -1};
int dy[4] = {1, 0, -1, 0};
const ll INF = 1e18;


struct Chord {
    int a, b;
};


struct Fenw {
    int n;
    vector<ll> fenw;
    Fenw(int n) : n(n), fenw(n+1,0) { }
    void update(int i, ll delta) {
        for(; i <= n; i += i & -i)
            fenw[i] += delta;
    }
    ll query(int i) {
        ll s = 0;
        for(; i; i -= i & -i)
            s += fenw[i];
        return s;
    }
    ll query(int l, int r) {
        return query(r) - query(l-1);
    }
};

int main(){
    int N, M;
    cin >> N >> M;
    vector<Chord> chords(M);
    REP(i,M){
        int a, b;
        cin >> a >> b;
        if(a > b) swap(a,b);
        chords[i] = {a, b};
    }
    // ソート：aが小さい順
    sort(chords.begin(), chords.end(), [](const Chord &c1, const Chord &c2){
        return c1.a < c2.a;
    });


    Fenw fenw(N);
    ll ans = 0;

    for (auto &c : chords) {

        if(c.a + 1 <= c.b - 1){
            ans += fenw.query(c.a+1, c.b-1);
        }

        fenw.update(c.b,1);
    }
    cout << ans << "\n";
}

Submission Info

Judge Result