r / c [terminology]

Terminology¶

Usage¶

• Use for row and column coordinates in matrix and grid algorithms.
• They may be loop variables, current coordinates, or recursive coordinates.
• Prefer them over row and col when the scope is compact.
• Do not use r simultaneously as both "row" and "right pointer" in the same scope.

m, n = len(mat), len(mat[0])
dist = [[-1] * n for _ in range(m)] # -1 means "not processed yet"
q = deque()
for r in range(m):
    for c in range(n):
        if mat[r][c] == 0:
            dist[r][c] = 0
            q.append((r, c))
# ...

See 542. 01 Matrix.