Best time to buy and sell stocks leetcode slow solution

stocks.py

def maxProfit(self, prices):
    valIndex = {}
    maxProfit = 0
    for i, price in enumerate(prices):
        if price not in valIndex:
            valIndex[price] = [i, i]
        else:
            valIndex[price][1] = i
    newprices = sorted(valIndex.keys())
    n = len(newprices)
    for j in range(n - 1, -1, -1):
        end = newprices[j]
        if end - newprices[0] <= maxProfit:
            break
        for i in range(j):
            curr = end - newprices[i]
            if curr <= maxProfit:
                break
            if valIndex[end][1] > valIndex[newprices[i]][0]:
                maxProfit = max(maxProfit, curr) 
    return maxProfit