33 lines
588 B
C++
33 lines
588 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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//母题
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//求n阶乘
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LL f(int n) {
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LL s = 1;
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for (int i = 1; i <= n; i++) s *= i;
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return s;
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}
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int main() {
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//INT_MAX
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//2147483647
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// s=1!+2!+3!+...+n!
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// 3!=3*2*1
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// 4!=4*3*2*1 四步
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// 4!=4*3! 一步，3！我知道
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//20!=20*19*18*....*1
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LL s = 0;
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for (int i = 1; i <= 20; i++) s += f(i);
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cout << s << endl;
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LL t = 1;
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s = 0;
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for (int i = 1; i <= 20; i++) t = t * i, s += t;
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cout << s << endl;
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return 0;
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} |