单调栈代码

//单调栈 数组实现 栈存的是下标 推荐这种方法
#include
using namespace std;
using ll = long long;
const int N = 2e5 + 9;
ll a[N], l[N], st[N], top;
 
void solve()
{
	int n; cin >> n;
	for (int i = 1; i <= n; ++i) cin >> a[i];
 
	for (int i = 1; i <= n; ++i)
	{
		while (top && a[st[top]] >= a[i]) top--;
		if (top) l[i] = a[st[top]];
		else l[i] = -1;
		st[++top] = i;
	}
	for (int i = 1; i <= n; ++i) cout << l[i] << " ";
}
 
int main()
{
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	solve();
	return 0;
}