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algorithm_interview_course/chapter_two/section_2.cpp

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+/* ************************************************************************
+> File Name:     algorithm_2.cpp
+> Author:        sunxiuyang
+> Mail:          sunxiuyang04@gmail.com 
+> Created Time:  Thu Jan 30 16:09:35 2020
+> Description:   
+ ************************************************************************/
+
+#include <iostream>
+#include <chrono>
+#include <thread>
+using namespace std;
+using namespace chrono;
+
+// O(n)
+void function1(long long n) {
+    long long k = 0;
+    for (long long i = 0; i < n; i++) {
+        k++;
+    }
+}
+
+// O(n^2)
+void function2(long long n) {
+    long long k = 0;
+    for (long long i = 0; i < n; i++) {
+        for (long j = 0; j < n; j++) {
+            k++;
+        }
+    }
+
+}
+
+// O(nlogn)
+void function3(long long n) {
+    long long k = 0;
+    for (long long i = 0; i < n; i++) {
+        for (long long j = 1; j < n; j = j*2) { // 注意这里j=1
+            k++;
+        }
+    }
+}
+
+
+void time_test() {
+    long long n; // 数据规模
+    while (cin>>n) {
+        milliseconds start_time = duration_cast<milliseconds >(
+            system_clock::now().time_since_epoch()
+        );
+
+        function3(n);
+
+        milliseconds end_time = duration_cast<milliseconds >(
+            system_clock::now().time_since_epoch()
+        );
+        cout << milliseconds(end_time).count() - milliseconds(start_time).count() 
+            <<" ms"<< endl;
+    }
+}
+
+int main() {
+    time_test();
+}
+