博客链接: http://codeshold.com/2017/02/c_code_sinped.html
编程的品味也有高低之分
1. 单链表元素删除操作
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低品位
remove_list_entry(entry) { prev = NULL; walk = entry; // Walk the list while(walk != entry) { prev = walk; walk = walk->next; } // Removing the entry by updating the previous or the head entry if(prev) { prev->next = entry->next; } else { head = entry->next; } } -
高品位
remove_list_entry(entry) { // The "indirect" pointer points to the ADDRESS of the thing we'll update indirect = &head; // Walk the list, looking for the thing points to the entry we want to remove while(*indirect != entry) { indirect = &(*indirect)->next; } // Remove the entry... *indirect = entry->next; }
2. 类型选择对程序执行时间的影响
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g++ test_int.cpp -O3编译运行#include <cstdio> #include <math.h> #include <ctime> #define NN 1000000 int main() { int t=clock(); long long sum=0; // 低品位, 运行时间明显长 for(long long a=1;a<=NN;a++) for(long long b=1;b<=sqrt(NN);b++) sum+=(a/b)*(a/b); printf("%lld,%d\n",sum,clock()-t); t=clock(); sum=0; // 高品位, 运行时间明显短 for(int a=1;a<=NN;a++) for(int b=1;b<=sqrt(NN);b++) sum+=(long long)(a/b)*(a/b); printf("%lld,%d\n",sum,clock()-t); }
