这是一种最容易想到的方法

import numpy as np
#a=np.random.randint(100,size=10)
a=[26, 69, 65, 99, 71, 51, 49, 54, 46, 23]

n=len(a)
c=a[n-2]+a[n-1]+a[n-3]
for i  in range(n):
    for j  in range(i,n):
        for k in range(max(i,j),n):
            if len(set([i,j,k]))==3 and a[i]+a[j]+a[k]==c:
                print( a[i],a[j],a[k],c)
                print(i,j,k)

0.0
[[1, 0, -1], [1, -1, 0], [0, -2, 2], [0, -2, 2]]