Interval & Math Target: 15s
Transpose + reverse-rows rotates 90 degrees clockwise in-place. Classic matrix manipulation.
n = len(m)
for i in range(n):
for j in range(i+1, n):
m[i][j], m[j][i] = m[j][i], m[i][j]
for row in m:
row.reverse()Type it from memory. Go.