'commit'

TangDou/LuoGuBook/第8章模拟与高精度/P1009_Prepare.cpp

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+#include <bits/stdc++.h>
+
+using namespace std;
+typedef long long LL;
+
+//母题
+//求n阶乘
+LL f(int n) {
+    LL s = 1;
+    for (int i = 1; i <= n; i++) s *= i;
+    return s;
+}
+
+int main() {
+    //INT_MAX
+    //2147483647
+    // s=1!+2!+3!+...+n!
+    // 3!=3*2*1
+    // 4!=4*3*2*1 四步
+    // 4!=4*3!    一步，3！我知道
+
+    //20!=20*19*18*....*1
+    LL s = 0;
+    for (int i = 1; i <= 20; i++) s += f(i);
+    cout << s << endl;
+
+
+    LL t = 1;
+    s = 0;
+    for (int i = 1; i <= 20; i++) t = t * i, s += t;
+    cout << s << endl;
+    return 0;
+}