Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/recursion-and-dynamic-programming/making-change.py

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+# Given an infinite supply of:
+#   - quarters
+#   - dimes
+#   - nickels
+#   - pennies
+# Write a function to count the number of ways to make change of n.
+
+def get(table, row, col):
+    """
+    Defensively get cell `row`, `col` from `table`.
+    """
+    if row < 0 or row >= len(table):
+        return 0
+    if col < 0 or col >= len(table[0]):
+        return 0
+    return table[row][col]
+
+def print_table(table):
+    print('\n'.join([
+        ','.join([str(col) for col in table[row]])
+        for row in range(len(table))]))
+
+def init_table(rows=0, cols=0, default=0):
+    result = []
+    for row in range(rows):
+        r = []
+        for col in range(cols):
+            r.append(default)
+        result.append(r)
+    return result
+
+def make_change(n):
+    coins = [1, 5, 10, 25]
+    table = init_table(rows=len(coins), cols=n)
+
+    for row in range(len(table)):
+        for col in range(len(table[row])):
+            curr_coin = coins[row]
+            curr_n = col + 1
+            # a
+            a = get(table, row - 1, col)
+            # b
+            b = get(table, row, curr_n - curr_coin - 1)
+            # c
+            c = 1 if curr_coin <= curr_n else 0
+            # commit
+            if curr_coin == curr_n:
+                table[row][col] = a + c
+            else:
+                table[row][col] = a + b * c
+            # debug
+            print_table(table)
+            print()
+    return table[-1][-1]
+
+print(make_change(7))