Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/coin.py

@@ -0,0 +1,50 @@
+def init_table(rows=0, cols=0, default=None):
+    table = []
+    for _ in range(rows):
+        row = []
+        for _ in range(cols):
+            row.append(default)
+        table.append(row)
+    return table
+
+def print_table(table):
+    result = ''
+    for row in range(len(table)):
+        x = ''
+        for col in range(len(table[row])):
+            x += str(table[row][col]) + ' '
+        result += x + '\n'
+    print(result)
+
+def get(table, row, col):
+    if row < 0 or col < 0:
+        return 0
+    else:
+        return table[row][col]
+
+def make_change(coins, amt):
+    table = init_table(rows=len(coins), cols=amt, default=0)
+    for row in range(len(table)):
+        for col in range(len(table[row])):
+            coin = coins[row]
+            curr_amt = col + 1
+            pull_down = get(table, row - 1, col)
+
+            if curr_amt < coin:
+                table[row][col] = pull_down
+            elif curr_amt == coin:
+                table[row][col] = pull_down + 1
+            else:
+                leftover = get(table, row, curr_amt - coin - 1)
+                table[row][col] = pull_down + leftover
+
+    print_table(table)
+    return table[-1][-1]
+
+#   1 2 3 4
+# 1 1 1 1 1
+# 2 1 1 2 2
+# 3 1 1 3 4
+
+result = make_change([3,2,1], 4)
+print(result)