# How Voting Systems Work 4, Exercise 1: a pairwise matrix for a five-candidate club vote
# 25 members rank five candidates (assumed, invented numbers).
# Print the matrix, then say whether a Condorcet winner exists and whether it won on first choices.
from collections import Counter

groups = [
    (7, ("Eve", "Dan", "Cy", "Bo", "Ana")),
    (6, ("Ana", "Bo", "Cy", "Dan", "Eve")),
    (5, ("Cy", "Dan", "Bo", "Eve", "Ana")),
    (4, ("Dan", "Cy", "Eve", "Bo", "Ana")),
    (3, ("Bo", "Cy", "Ana", "Dan", "Eve")),
]
ballots = [r for count, r in groups for _ in range(count)]
n = len(ballots)
names = sorted(ballots[0])
wins = {(x, y): sum(1 for b in ballots if b.index(x) < b.index(y))
        for x in names for y in names if x != y}
print("      " + "".join(f"{y:>5}" for y in names))
for x in names:
    print(f"{x:>5} " + "".join(f"{'-' if x == y else wins[x, y]:>5}" for y in names))
winner = next((x for x in names if all(wins[x, y] > n / 2 for y in names if y != x)), None)
print("Condorcet winner:", winner)
first = Counter(b[0] for b in ballots)
print("first choices:", dict(sorted(first.items())))
print("top on first choices:", first.most_common(1)[0][0])

# Output when run:
#         Ana   Bo   Cy  Dan  Eve
#   Ana     -    6    6    9    9
#    Bo    19    -    9    9   14
#    Cy    19   16    -   14   18
#   Dan    16   16   11    -   18
#   Eve    16   11    7    7    -
# Condorcet winner: Cy
# first choices: {'Ana': 6, 'Bo': 3, 'Cy': 5, 'Dan': 4, 'Eve': 7}
# top on first choices: Eve