P5788 【模板】单调栈

https://www.luogu.com.cn/record/91963289

Luogu/P5788/P5788.cpp

@@ -1,24 +1,36 @@
-#include <bits/stdc++.h>
+#include <iostream>
+#include <stack>
 
-using namespace std;
+using std::cin;
+using std::cout;
+const char endl = '\n';
 
-int n, a[3000005], f[3000005];
-stack<int> st;
+const int N = 3e6 + 5;
+
+int n, a[N], f[N];
+std::stack<int> st;
 
 int main() {
     std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
     cin >> n;
+
     for (int i = 1; i <= n; i++) {
         cin >> a[i];
     }
-    for (int i = n; i >= 1; i--) {
+
+    for (int i = n; i; i--) {
         while (!st.empty() && a[st.top()] <= a[i]) st.pop();
         f[i] = st.empty() ? 0 : st.top();
-        st.push(i);
+        st.emplace(i);
     }
+
     for (int i = 1; i <= n; i++) {
         cout << f[i] << ' ';
     }
+
     cout << endl;
+
     return 0;
 }