diff --git a/3sem/data structures and algos/01/program.cpp b/3sem/data structures and algos/01/program.cpp
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+++ b/3sem/data structures and algos/01/program.cpp	
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+// dsaa_01.cpp
+// Горбацевич Андрей
+#include <iostream>
+#include <cmath>
+#include <chrono>
+
+typedef double long_type;
+
+void time_passed(std::chrono::system_clock::time_point start, long_type& holder);
+void test(int N);
+void algo_01(int N, long_type& out_val);  // Naive way
+void algo_02(int N, long_type& out_val);  // Somewhat efficient way
+
+int main() {
+    int i;
+    std::cout << "N=";
+    std::cin >> i;
+
+    test(i);
+
+    return 0;
+}
+
+inline void time_passed(std::chrono::system_clock::time_point start, long_type& holder) {
+    auto stop = std::chrono::high_resolution_clock::now();
+    auto duration = std::chrono::duration_cast<std::chrono::microseconds>(stop - start);
+    holder = duration.count();
+}
+
+void test(int N) {
+    long_type fft, sft = fft = 0;
+    long_type ffv, sfv = ffv = 0;
+
+    {
+        auto start = std::chrono::high_resolution_clock::now();
+        algo_01(N, ffv);
+        time_passed(start, fft);
+    }
+    {
+        auto start = std::chrono::high_resolution_clock::now();
+        algo_02(N, sfv);
+        time_passed(start, sft);
+    }
+
+    printf(
+        "algo_01 is %s than algo_02 by %.0f microseconds (%.0f against %.0f; N=%d; %.0f; %.0f)\n"
+        "Sum of i! from 1 to %d = %.0f",
+        (fft > sft? "slower" : "faster"), fabs(fft - sft), fft, sft, N, ffv, sfv, N, ffv
+    );
+}
+
+void algo_01(int N, long_type& out_val) {  // O(N^2)
+    long_type sum = 0;
+
+    for (int k = 1; k <= N; k++) {  // O(N)
+        long_type acc = 1;
+        for (int i = 1; i <= k; i++) {  // O(N)
+            acc *= i;
+        }
+        sum += acc;
+    }
+
+    out_val = sum;
+}
+
+void algo_02(int N, long_type& out_val) {  // O(N)
+    long_type sum = 0;
+    long_type acc = 1;
+
+    for (int k = 1; k <= N; k++) {  // O(N)
+        sum += (acc *= k);
+    }
+
+    out_val = sum;
+}
+// Вычислить суммы факториалов K первых целых чисел для K=1..N
diff --git a/3sem/data structures and algos/01/аисд отчёт прак 1.pdf b/3sem/data structures and algos/01/аисд отчёт прак 1.pdf
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