'commit'

TangDou/LuoGuBook/第8章模拟与高精度/P1009_3.cpp

@@ -0,0 +1,47 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+vector<int> add(vector<int> A, vector<int> B) {
+    if (A.size() < B.size()) swap(A, B);
+    vector<int> C;
+    int t = 0;
+    for (int i = 0; i < A.size(); i++) {
+        t += A[i];
+        if (i < B.size()) t += B[i];
+        C.push_back(t % 10);
+        t /= 10;
+    }
+    if (t) C.push_back(t);
+    return C;
+}
+
+vector<int> mul(vector<int> A, int b) {
+    vector<int> C;
+    int t = 0;
+    // 8899 * 2 = 17798
+    for (int i = 0; i < A.size() || t; i++) {
+        if (i < A.size()) t += A[i] * b;
+        C.push_back(t % 10);
+        t /= 10;
+    }
+    while (C.size() > 1 && C.back() == 0) C.pop_back();
+    return C;
+}
+
+int main() {
+    int n;
+    cin >> n;
+    vector<int> F, RES;
+    //初始化
+    RES.push_back(0);
+    F.push_back(1);
+    for (int i = 1; i <= n; i++) { //
+        F = mul(F, i);
+        RES = add(RES, F);
+    }
+    //倒序输出
+    for (int i = RES.size() - 1; i >= 0; i--)
+        printf("%d", RES[i]);
+    return 0;
+}