代码

#include <bits/stdc++.h>
using namespace std;
int n, ans, a[333], b[333], c[333];
void dfs(int x) {
	if (x == n + 1) {
		for (int i = 1; i <= n; i++) {
			int j = i, k = i;
			while (j >= 2 && c[j - 1] <= c[i]) j--;
			while (k <= n - 1 && c[k + 1] < c[i]) k++;
			if (abs((i - j) - (k - i)) > 2) return ;
		}
		ans++;
		return ;
	}
	for (c[x] = a[x]; c[x] <= b[x]; c[x]++)
		dfs(x + 1);
}
int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) cin >> a[i] >> b[i];
	dfs(1);
	cout << ans << endl;
	return 0;
}

评测结果