Problem8212--[yosupo] Graph - Matching on General Graph

8212: [yosupo] Graph - Matching on General Graph

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Time Limit : 1.000 sec  Memory Limit : 256 MiB  Special Judge

Description

Given a simple undirected graph with $N$ vertices and $M$ edges. $i$-th edge is $(u_i, v_i)$.
Calculate the maximum matching.

Input

$N$ $M$
$u_0$ $v_0$
$u_1$ $v_1$
:
$u_{M - 1}$ $v_{M - 1}$

Output

$X$
$a_0$ $b_0$
$a_1$ $b_1$
:
$a_{X - 1}$ $b_{X - 1}$
$X$ is the size of the maximum matching.

Constraints

$1 \leq N \leq 500$
$0 \leq M \leq \frac{N(N-1)}{2}$
$0 \leq u_i, v_i < N$

Sample 1 Input

7 8
2 0
0 5
5 6
6 1
1 0
1 3
3 4
1 4

Sample 1 Output

3
0 2
1 6
3 4

Sample 2 Input

5 4
0 1
0 2
0 3
0 4

Sample 2 Output

1
0 1

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