autotest

Extra
Test 1/1
Your result: 4
Right result: 3
break_rings(({8,7},{1,9},{2,7},{3,6},{1,7},{5,7},{3,4},{9,5},{9,6},{3,5},))

console out

>>> break_rings(({8,7},{1,9},{2,7},{3,6},{1,7},{5,7},{3,4},{9,5},{9,6},{3,5},))
[[8, 7], [9, 1], [2, 7], [3, 6], [1, 7], [5, 7], [3, 4], [9, 5], [9, 6], [3, 5]]
ring_count: {1: 2, 2: 1, 3: 3, 4: 1, 5: 3, 6: 2, 7: 4, 8: 1, 9: 3}
ring_count: {1: 2, 2: 1, 3: 3, 4: 1, 5: 3, 6: 2, 7: 4, 8: 1, 9: 3}
max: 7
ring_list: [[8], [9, 1], [2], [3, 6], [1], [5], [3, 4], [9, 5], [9, 6], [3, 5]]
ring_count: {1: 2, 2: 1, 3: 3, 4: 1, 5: 3, 6: 2, 8: 1, 9: 3}
ring_count: {1: 2, 2: 1, 3: 3, 4: 1, 5: 3, 6: 2, 8: 1, 9: 3}
max: 3
ring_list: [[8], [9, 1], [2], [1], [5], [9, 5], [9, 6]]
ring_count: {1: 2, 2: 1, 5: 2, 6: 1, 8: 1, 9: 3}
ring_count: {1: 2, 2: 1, 5: 2, 6: 1, 8: 1, 9: 3}
max: 9
ring_list: [[8], [2], [1], [5]]
ring_count: {8: 1, 1: 1, 2: 1, 5: 1}
<<< 3

code

def break_rings(rings):
    rings_list = []
    removed = 0
    for ring in rings:
        if len(ring) == 2: rings_list.append(list(ring))
    print(rings_list)
    len_ = len(rings)
    while max(count_rings(rings_list,len_).values()) > 1:
        count = count_rings(rings_list,len_)
        max_ = max(count, key=count.get)
        print('max: ',max_)
        rings_list = update_rings(rings_list, max_)
        removed += 1
    for i in rings_list:
        if len(i) > 1: removed += 1
    return removed

def count_rings(rings, len_):
    ring_count = {}
    for i in range(1,len_+1):
        for ring in rings:
            if i in ring:
                try:
                    ring_count[i] += 1
                except KeyError:
                    ring_count.update({i: 1})
    print('ring_count: ',ring_count)
    return ring_count

def update_rings(rings, remove):
    rings_list = []
    for ring in rings:
        if ring[0] == remove: continue
        try:
            ring.remove(remove)
            rings_list.append(list(ring))
        except ValueError:
            rings_list.append(list(ring))
    print('ring_list: ',rings_list)
    return rings_list

if __name__ == '__main__':
    # These "asserts" using only for self-checking and not necessary for auto-testing
    assert break_rings(({1, 2}, {2, 3}, {3, 4}, {4, 5}, {5, 6}, {4, 6})) == 3, "example"
    assert break_rings(({1, 2}, {1, 3}, {1, 4}, {2, 3}, {2, 4}, {3, 4})) == 3, "All to all"
    assert break_rings(({5, 6}, {4, 5}, {3, 4}, {3, 2}, {2, 1}, {1, 6})) == 3, "Chain"
    assert break_rings(({8, 9}, {1, 9}, {1, 2}, {2, 3}, {3, 4}, {4, 5}, {5, 6}, {6, 7}, {8, 7})) == 5, "Long chain"

From: http://www.checkio.org/mission/break-rings/solve/

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