带权中位数-算法导论第三版第九章思考题9-2
b
时间复杂度O(nlgn)
float find_median_with_weights_b(float *array,int length)
{quick_sort<float>(array,0,length-1);float sum = 0;int index = 0;while (sum < 0.5){sum += array[index];index++;}return array[index-1];
}
辅助代码quick_sort
链接地址
c
时间复杂度Θ(n)
float find_median_with_weights_c(float *array,int start,int end,float last_left_sum,float last_right_sum)
{select<float>(array,start,end,(end - start)/2);float left_sum = 0;float right_sum = 0;for (int i = start; i < start + (end - start)/2; ++i) {left_sum += array[i];}for (int i = start + (end - start)/2 + 1 ;i < end+1; ++i) {right_sum+=array[i];}if(left_sum+last_left_sum < 0.5 && right_sum +last_right_sum< 0.5){return array[start + (end - start)/2];}else if(left_sum>0.5){last_right_sum += right_sum;end = (end - start)/2 - 1;}else{last_left_sum += left_sum;start = start + (end - start)/2;}return find_median_with_weights_c(array,start,end,last_left_sum,last_right_sum);
}
float find_median_with_weights_c(float *array,int length)
{return find_median_with_weights_c(array,0,length-1,0,0);
}
辅助代码select
链接地址
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