Stack Discipline Target: 15s
Next-greater-element uses a decreasing stack. Shows up in stock span and temperature problems.
result = [-1] * len(a)
stack = []
for i in range(len(a) - 1, -1, -1):
while stack and stack[-1] <= a[i]:
stack.pop()
if stack:
result[i] = stack[-1]
stack.append(a[i])Type it from memory. Go.