问如何按升序显示Y上的值，但保存其索引。Matplotlib

EN

import numpy as np
import matplotlib.pyplot as plt
x=[]
with open('D:\Programming\Contest\stepperf.txt','r') as a:
    for line in a:
        x.append(line.strip())
x =np.array(x)
y=[]
with open('D:\Programming\Contest\Hall.txt','r') as b:
    for line in b:
        y.append(line.strip())
y  = np.array(y)


fig, ax = plt.subplots(figsize=(8, 6))
plt.grid()     
plt.plot(x,y) 

plt.show()