算法时间复杂度对比

题目:求1-1/x+1/x^2-1/x^3+......+1/(-x)^(n-1)

算法一:

#include<stdio.h>
#include<sys/timeb.h>
void main(){
    timeb t1,t2;
    long t;
    double x,sum=1,sum1;
    int i,j,n;
    printf("请输入x n:");
    scanf("%lf%d",&x,&n);
    ftime(&t1);
    for (i=1;i<=n;i++)
    {
        sum1=1;
        for(j=1;j<=i;j++)
             sum1=sum1*(-1.0/x);
        sum+=sum1;
    }

    ftime(&t2);
    t=(t2.time-t1.time)*1000+(t2.millitm-t1.millitm);
    printf("sum=%lf用时%ld毫秒\n",sum,t);
}

时间复杂度:

算法2：

#include<stdio.h>
#include<sys/timeb.h>
void main(){
    timeb t1,t2;
    long t;
    double x,sum=1,sum1=1;
    int i,j,n;
    printf("请输入x n:");
    scanf("%lf%d",&x,&n);
    ftime(&t1);
    for (i=1;i<=n;i++)
    {
        sum1*=(-1.0/x);
        sum+=sum1;
    }

    ftime(&t2);
    t=(t2.time-t1.time)*1000+(t2.millitm-t1.millitm);
    printf("sum=%lf用时%ld毫秒\n",sum,t);
}

时间复杂度:

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