24 lines
499 B
C++
24 lines
499 B
C++
#include <bits/stdc++.h>
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using namespace std;
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typedef long long LL;
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//高精度+高精度
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//高精度*低精度
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int main() {
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int n;
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cin >> n;
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LL res = 0;
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LL f = 1;
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for (int i = 1; i <= n; i++) {
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// f =i!
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// 3!= 3*2*1
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// 4!=4*3*2*1
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f *= i; //计算i! =(i-1)! * i 举栗子： 4!= 4* 3!
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res += f; //计算阶乘的和 res= 1!+2!+3!+...+n!
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}
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//输出要需要改
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cout << res << endl;
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return 0;
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} |