C++实例

我们先给一个实例，在windows系统下，使用VisualStudio的debug模式，编译和运行程序：

#include <algorithm>
#include <ctime>
#include <iostream>int main(){// Generate dataconst unsigned arraySize = 32768;int data[arraySize];for (unsigned c = 0; c < arraySize; ++c)data[c] = std::rand() % 256;// Testclock_t start = clock();long long sum = 0;for (unsigned i = 0; i < 100000; ++i){for (unsigned c = 0; c < arraySize; ++c){   // Primary loop.if (data[c] >= 128)sum += data[c];}}double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC;std::cout << elapsedTime << '\n';std::cout << "sum = " << sum << '\n';}

执行结果如下：

12.474
sum = 312275400000

如果我们在处理数据前加上一个排序算法：

#include <algorithm>
#include <ctime>
#include <iostream>int main(){// Generate dataconst unsigned arraySize = 32768;int data[arraySize];for (unsigned c = 0; c < arraySize; ++c)data[c] = std::rand() % 256;std::sort(data, data + arraySize);// Testclock_t start = clock();long long sum = 0;for (unsigned i = 0; i < 100000; ++i){for (unsigned c = 0; c &