simulation

[KevinACoder]

"""  1041. Robot Bounded In Circle """
def isRobotBounded(instructions):
    x = 0
    y = 0
    dir = 0 #direction - N W S E
    #offset for each direction
    dx = [0, -1, 0, 1]
    dy = [1, 0, -1, 0]
    for c in instructions:
        if c == 'G': #go ahead by dir
            x += dx[dir]
            y += dy[dir]
        elif c == 'L': #turn left
            dir = (dir + 3)%4
        elif c == 'R': #turn right
            dir = (dir + 1)%4
    return (x == 0 and y == 0) or dir != 0 #if go back to origin or not facing north

[KevinACoder]

""" 838. Push Dominoes """   
def pushDominoes(D):
    max_int = 9999999
    #record the distance from current dominoe to nearest push down one(left and right)
    left_steps = [max_int for x in range(len(D))]
    right_steps = [max_int for x in range(len(D))]

    for i in range(len(D)):
        if D[i] == 'L':
            #if occur one push down domine
            left_steps[i] = 0
            #for all following domine that influenced
            for j in range(i-1, -1, -1):
                if D[j] != '.': #only influence '.'
                    break
                left_steps[j] = left_steps[j+1]+1
        elif D[i] == 'R':
            right_steps[i] = 0
            for j in range(i+1, len(D)):
                if D[j] != '.':
                    break
                right_steps[j] = right_steps[j-1]+1

    #simulate the push work
    ND = ''
    for i in range(len(D)):
        if left_steps[i] < right_steps[i]:
            ND += 'L'
        elif left_steps[i] > right_steps[i]:
            ND += 'R'
        else:
            ND += '.'

    return ND

[KevinACoder]

""" 38. Count and Say """    
def say(ns):
    ans = ''
    s = 0
    leng = len(ns)
    for e in range(1, leng+1):
        if e == leng or ns[s] != ns[e]:   
            cnt = e - s
            ans += str(cnt)
            ans += ns[s]
            s = e
    return ans

def countAndSay(n):
    ans = '1'
    for _ in range(1, n):
        ans = say(ans)
    return ans

[KevinACoder]

""" 54. Spiral Matrix """
def spiralOrder(mat):
    ans = []
    if len(mat) == 0: return ans
    #direction of move
    dir = 0 # R, D, L, U
    #walls of visit [left, right), [up, down)
    left = 0
    right = len(mat[0]) - 1 #in case of access out of boundary
    up = 0
    down = len(mat) - 1
    num = len(mat)*len(mat[0])
    #loop until all mat elements have been put in ans
    x = 0
    y = 0
    #
    #     ----->
    #    |      |
    #     <-----      
    while len(ans) < num:
        if dir == 0:
            while y < right: #the right most element remained to access in next dir
                ans.append(mat[x][y])
                y += 1
            up += 1
        elif dir == 1:
            while x < down:
                ans.append(mat[x][y])
                x += 1
            right -= 1
        elif dir == 2:
            while y > left:
                ans.append(mat[x][y])
                y -= 1
            down -= 1
        else:
            while x > up:
                ans.append(mat[x][y])
                x -= 1
            right += 1
        dir = (dir + 1)%4 #adjust visit direction

    #include the central element
    return ans

"""     if len(ans) != num:
        ans.append(mat[x][y]) """

[KevinACoder]

""" 989. Add to Array-Form of Integer """
def addToArrayForm(nums, k):
    nums.reverse()
    ans = []
    for i in range(len(nums)):
        k += nums[i]
        ans.append(k%10)
        k //= 10

    while k > 0:
        ans.append(k%10)
        k //= 10

    ans.reverse()
    return ans