【枚举区间】CF Edu10 C

Problem - C - Codeforces

题意：

思路：

应该反思一下这么典的思路为什么会想不到

枚举区间，一个很经典的套路是，枚举 l，对 r 计数

对于一个l，r取这么多限制中离 l 最近的那个

Code：

#include <bits/stdc++.h>

#define int long long

using i64 = long long;

constexpr int N = 3e5 + 10;
constexpr int M = 3e5 + 10;
constexpr int P = 2e6;
constexpr i64 Inf = 1e18;
constexpr int mod = 1e9 + 7;
constexpr double eps = 1e-6;

int n, m;
int a[N], pos[N], r[N];

void solve() {
    std::cin >> n >> m;
    for (int i = 1; i <= n; i ++) {
        std::cin >> a[i];
        pos[a[i]] = i;
        r[i] = n;
    }

    for (int i = 1; i <= m; i ++) {
        int x, y;
        std::cin >> x >> y;
        if (pos[x] > pos[y]) std::swap(x, y);
        r[pos[x]] = std::min(pos[y] - 1, r[pos[x]]);
    }

    for (int i = n - 1; i >= 1; i --) {
        r[i] = std::min(r[i], r[i + 1]);
    }

    int ans = 0;
    for (int i = 1; i <= n; i ++) ans += r[i] - i + 1;
    std::cout << ans << "\n";
}
signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t = 1;

    while (t--) {
        solve();
    }
    
    return 0;
}