#include <iostream>#include <cmath>#include <ctime>using namespace std;const int MAX = 10000;int a[MAX];int main(){ int i, j, n = MAX; int rep = 60; //重复次数 clock_t beg, end; for (i = 0; i < n; i++) a[i] = rand() % 20000 - 10000; //-10000 <= a[i]< 10000 cout << "test fabs" << endl; beg = clock(); for (j = 0; j < rep; j++) for (i = 0; i < n; i++) a[i] =fabs(a[i]); end = clock(); cout << "time: " << end - beg << "ms" << endl; cout << "test if else" << endl; beg = clock(); for (j = 0; j < rep; j++) for (i = 0; i < n; i++) { if (a[i] < 0) a[i] = -a[i]; } end = clock(); cout << "time: " << end - beg << "ms" << endl; return 0;}
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