洛谷 P1338 末日的传说

可以说是超难的一道题了。。。。
全程题解：
https://www.luogu.org/blog/user11765/solution-p1338

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#include<iostream>
#include<algorithm>
using namespace std;
long long n, m, a[50005];
int main() {
cin >> n >> m;
long long s = 1, e = n;
for (long long i = 1; i <= n; i++) {
long long t = (n - i)*(n - i - 1) / 2;
if (t >= m)a[s++] = i;
else {
a[e--] = i;
m -= e - s + 1;
}
}
for (int i = 1; i <= n; i++)cout << a[i] << " ";
}