CF1176E n/2 点覆盖

main/1100-1199/1176E.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"bufio"
+	. "fmt"
+	"io"
+)
+
+// https://space.bilibili.com/206214
+func CF1176E(_r io.Reader, _w io.Writer) {
+	in := bufio.NewReader(_r)
+	out := bufio.NewWriter(_w)
+	defer out.Flush()
+
+	var T, n, m, v, w int
+	for Fscan(in, &T); T > 0; T-- {
+		Fscan(in, &n, &m)
+		g := make([][]int, n+1)
+		for ; m > 0; m-- {
+			Fscan(in, &v, &w)
+			g[v] = append(g[v], w)
+			g[w] = append(g[w], v)
+		}
+		vis := make([]bool, len(g))
+		a := [2][]int{}
+		var f func(int, int)
+		f = func(v, d int) {
+			vis[v] = true
+			a[d] = append(a[d], v)
+			for _, w := range g[v] {
+				if !vis[w] {
+					f(w, d^1)
+				}
+			}
+		}
+		f(1, 0)
+		ans := a[0]
+		if len(a[0]) > len(a[1]) {
+			ans = a[1]
+		}
+		Fprintln(out, len(ans))
+		for _, v := range ans {
+			Fprint(out, v, " ")
+		}
+		Fprintln(out)
+	}
+}
+
+//func main() { CF1176E(os.Stdin, os.Stdout) }

main/1100-1199/1176E_test.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"github.com/EndlessCheng/codeforces-go/main/testutil"
+	"testing"
+)
+
+// https://codeforces.com/contest/1176/problem/E
+// https://codeforces.com/problemset/status/1176/problem/E
+func TestCF1176E(t *testing.T) {
+	// just copy from website
+	rawText := `
+inputCopy
+2
+4 6
+1 2
+1 3
+1 4
+2 3
+2 4
+3 4
+6 8
+2 5
+5 4
+4 3
+4 1
+1 3
+2 3
+2 6
+5 6
+outputCopy
+2
+1 3
+3
+4 3 6`
+	testutil.AssertEqualCase(t, rawText, 0, CF1176E)
+}