CF1971H 2-SAT

Author: EndlessCheng

main/1900-1999/1971H.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"bufio"
+	. "fmt"
+	"io"
+)
+
+// https://space.bilibili.com/206214
+func cf1971H(in io.Reader, _w io.Writer) {
+	out := bufio.NewWriter(_w)
+	defer out.Flush()
+
+	var T, n int
+o:
+	for Fscan(in, &T); T > 0; T-- {
+		Fscan(in, &n)
+		a := [3][]int{}
+		for i := range a {
+			a[i] = make([]int, n)
+			for j := range a[i] {
+				Fscan(in, &a[i][j])
+			}
+		}
+
+		g := make([][]int, n*2)
+		addEdge := func(x, a, y, b int) {
+			if x < 0 {
+				x = -x
+				a ^= 1
+			}
+			if y < 0 {
+				y = -y
+				b ^= 1
+			}
+			v, w := x-1+a*n, y-1+b*n
+			g[v] = append(g[v], w)
+		}
+		for j := 0; j < n; j++ {
+			for p := 0; p < 3; p++ {
+				for q := 0; q < 3; q++ {
+					if q != p {
+						addEdge(a[p][j], 0, a[q][j], 1)
+					}
+				}
+			}
+		}
+
+		sid := make([]int, len(g))
+		dfn := make([]int, len(g))
+		clock := 0
+		st := []int{}
+		inSt := make([]bool, len(g))
+		var tarjan func(int) int
+		tarjan = func(v int) int {
+			clock++
+			dfn[v] = clock
+			lowV := clock
+			st = append(st, v)
+			inSt[v] = true
+			for _, w := range g[v] {
+				if dfn[w] == 0 {
+					lowW := tarjan(w)
+					lowV = min(lowV, lowW)
+				} else if inSt[w] {
+					lowV = min(lowV, dfn[w])
+				}
+			}
+			if dfn[v] == lowV {
+				for {
+					w := st[len(st)-1]
+					st = st[:len(st)-1]
+					inSt[w] = false
+					sid[w] = v
+					if w == v {
+						break
+					}
+				}
+			}
+			return lowV
+		}
+		for i, ts := range dfn {
+			if ts == 0 {
+				tarjan(i)
+			}
+		}
+		for i, id := range sid[:n] {
+			if id == sid[i+n] {
+				Fprintln(out, "NO")
+				continue o
+			}
+		}
+		Fprintln(out, "YES")
+	}
+}
+
+//func main() { cf1971H(bufio.NewReader(os.Stdin), os.Stdout) }

main/1900-1999/1971H_test.go

@@ -0,0 +1,38 @@
+// Generated by copypasta/template/generator_test.go
+package main
+
+import (
+	"github.com/EndlessCheng/codeforces-go/main/testutil"
+	"testing"
+)
+
+// https://codeforces.com/contest/1971/problem/H
+// https://codeforces.com/problemset/status/1971/problem/H
+func Test_cf1971H(t *testing.T) {
+	testCases := [][2]string{
+		{
+			`4
+4
+1 -2 -3 -2
+-4 4 -1 -3
+1 2 -2 4
+2
+1 2
+-1 -2
+2 -2
+5
+1 2 3 4 5
+-2 3 -4 -5 -1
+3 -5 1 2 2
+6
+1 3 -6 2 5 2
+1 3 -2 -3 -6 -5
+-2 -1 -3 2 3 1`,
+			`YES
+NO
+YES
+NO`,
+		},
+	}
+	testutil.AssertEqualStringCase(t, testCases, 0, cf1971H)
+}