AtCoder problem 017

C++ solution:


Python solution: # でつoO(YOU PLAY WITH THE CARDS YOU'RE DEALT..)
import sys
def main():
    input = sys.stdin.readline
    N, M = map(int, input().split())
    S = [[] for _ in range(N)]
    T = [[] for _ in range(N)]
    E = []
    for i in range(M):
        s, t = map(lambda x: int(x) - 1, input().split())
        S[s].append(i)
        T[t].append(i)
        E.append((s, t))
    st = SegmentTree(N, f=lambda a, b: a + b)
    ans = 0
    for n in range(N):
        for i in T[n]:
            s, t = E[i]
            st.modify_at(s, -1)
        for i in T[n]:
            s, t = E[i]
            ans += st.query(s + 1, t)
        st.modify_at(n, len(S[n]))
    print(ans)

class SegmentTree:
    __slots__ = ('__n', '__d', '__f', '__e')

    def __init__(self, n=None, f=max, identity_factory=int, initial_values=None):
        assert(n or initial_values)
        size = n if n else len(initial_values)
        d = [identity_factory() for _ in range(2 * size + 1)]
        self.__n, self.__d, self.__f, self.__e = size, d, f, identity_factory
        if initial_values:
            for i, v in enumerate(initial_values): d[size + i] = v
            for i in range(size - 1, 0, -1): d[i] = f(d[i << 1], d[i << 1 | 1])

    def __repr__(self) -> str:
        n = self.__n
        return str([self.get_at(i) for i in range(n)])

    def get_at(self, index):
        return self.__d[index + self.__n]

    def set_at(self, index, new_value):
        i, d, f = index + self.__n, self.__d, self.__f
        if d[i] == new_value: return
        d[i], i = new_value, i >> 1
        while i: d[i], i = f(d[i << 1], d[i << 1 | 1]), i >> 1

    def modify_at(self, index, value):
        self.set_at(index, self.__f(self.__d[index + self.__n], value))

    def query(self, from_inclusive, to_exclusive):
        ans = self.__e()
        if to_exclusive <= from_inclusive: return ans
        l, r, d, f = from_inclusive + self.__n, to_exclusive + self.__n, self.__d, self.__f
        while l < r:
            if l & 1: ans, l = f(ans, d[l]), l + 1
            if r & 1: ans, r = f(d[r - 1], ans), r - 1
            l, r = l >> 1, r >> 1
        return ans

    def query_all(self):
        return self.__d[1]

    def bisect_left(self, func, from_inclusive=None, to_exclusive=None):
        '''func()がTrueになるもっとも左のindexを探す
        '''
        n, f, d, v = self.__n, self.__f, self.__d, self.__e()
        l = (from_inclusive if from_inclusive else 0) + n
        r = (to_exclusive if to_exclusive else n) + n
        h = 0
        while l < r:
            if l & 1:
                nv = f(v, d[l])
                if func(nv): return self.__single_bisect_left(func, l, v)
                v, l = nv, l + 1
            l, r, h = l >> 1, r >> 1, h + 1
        if r == 0: return n
        for i in range(h, 0, -1):
            if ((r + 1) << i <= n + n):
                nv = f(v, d[r])
                if func(nv): return self.__single_bisect_left(func, r, v)
                v, r = nv, r + 1
            r <<= 1
        return n

    def __single_bisect_left(self, func, root, left_val):
        n, f, d = self.__n, self.__f, self.__d
        i, v = root, left_val
        while i < n:
            i <<= 1
            nv = f(v, d[i])
            if not func(nv): i, v = i + 1, nv
        return i - n

if __name__ == '__main__':
    main()





Ruby solution: class OnlineSum
    def initialize(n)
        @n = 2 ** Math.log2(n).ceil
        @data = [0] * @n
    end

    def inc(i)
        m = 1
        while m <= @n
            @data[i] += 1 if (i & m) == 0
            i |= m; m <<= 1
        end
    end

    def sum(i)
        i += 1
        m = 1
        acc = 0
        while i > 0
            acc += @data[i - 1] if (i & m) != 0
            i &= ~m; m <<= 1
        end
        acc
    end
end

def main
    n, m = readline.split.map(&:to_i)

    graph = Array.new(n) { [] }
    m.times do
        a, b = readline.split.map(&:to_i)
        graph[a - 1].push(b - 1)
    end
    os = OnlineSum.new(n)
    ans = 0
    for u in 0...n
        graph[u].sort!.reverse!
        for v in graph[u]
            ans += os.sum(v - 1) - os.sum(u)
            os.inc(v)
        end
    end
    puts ans
end

main if __FILE__ == $0