hackerrank-common-child.py

frstWord = list(input().strip())
scndWord = list(input().strip())

def longestChild(frst, scnd):
    grid = [[0 for _ in range(len(scnd)+1)] for _ in range(len(frst)+1)]
    result = 0

    for i in range(len(frst)+1):
        for j in range(len(scnd)+1):
            if i == 0 or j == 0:
                grid[i][j] = 0
            elif frst[i-1] == scnd[j-1]:
                grid[i][j] = grid[i-1][j-1] + 1
                result = max(result, grid[i][j])
            else:
                grid[i][j] = max(grid[i-1][j], grid[i][j-1]) 
    return result

print(longestChild(frstWord, scndWord))