memset初始化值的效率秒杀for循环

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">在一亿数据的赋值下，memset使用了1ms,而for循环使用了136ms</span>

贴上代码：

#include <string.h>
#include <iostream>
#include <string>
#include <iostream>
#define MAXSIZE 10000
using namespace std;
#include <time.h>
#include <sys/timeb.h>
int get_time(string r)
{
    struct timeb rawtime;
    ftime(&rawtime);
    static int ms = rawtime.millitm;
    static unsigned long s = rawtime.time;
    int out_ms = rawtime.millitm - ms;
    unsigned long out_s = rawtime.time - s;
    if (out_ms < 0)
    {
        out_ms += 1000;
        out_s -= 1;
    }
    ms = rawtime.millitm;
    s = rawtime.time;
    int total = 1000*out_s+out_ms;
    cout<<r<<": "<<total<<"ms"<<endl;
    return total;
}


int main()
{
int (*arr)[MAXSIZE]=new int[MAXSIZE][MAXSIZE]; //MAXSIZE 10000
get_time("memset begin");
memset(arr,'9',sizeof(arr));
get_time("memset end");
get_time("for begin");
for(int i=0;i<MAXSIZE;++i)
for(int j=0;j<MAXSIZE;++j)arr[i][j]=99;
get_time("for end");
delete[] arr;
return 0;
}

转载于:https://www.cnblogs.com/freeopen/p/5482946.html