1!+2!+3!+...+n!和的后6位

D.cpp

@@ -0,0 +1,20 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+const int MOD = 1000000;
+
+int main() {
+    int n;
+    cin >> n;
+    if (n > 24)n = 24;//注意到25!末尾已经有6个0不会对计算结果产生影响
+    int s = 0;
+    for (int i = 1; i <= n; i++) {
+        int p = 1;
+        for (int j = 2; j <= i; j++) {
+            p = p * j % MOD;
+        }
+        s = (s + p) % MOD;
+    }
+    cout << s << endl;
+    return 0;
+}