[1900][1A] CF1585D 结论题 三置换 排序

Author: EndlessCheng

main/1500-1599/1585D.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"bufio"
+	. "fmt"
+	"io"
+)
+
+// github.com/EndlessCheng/codeforces-go
+func CF1585D(_r io.Reader, _w io.Writer) {
+	in := bufio.NewReader(_r)
+	out := bufio.NewWriter(_w)
+	defer out.Flush()
+
+	var T, n int
+	for Fscan(in, &T); T > 0; T-- {
+		Fscan(in, &n)
+		a := make([]int, n+1)
+		p := make([]int, n+1)
+		eq := false
+		for i := 1; i <= n; i++ { // 注意 a 从 1 开始
+			Fscan(in, &a[i])
+			if p[a[i]] > 0 {
+				eq = true
+			}
+			p[a[i]] = i
+		}
+		if eq || n < 2 {
+			Fprintln(out, "YES")
+			continue
+		}
+		for i := 1; i < n-1; i++ {
+			if p[i] == i {
+				continue
+			}
+			x, y := p[i], i
+			z := n
+			if x == n {
+				z--
+			}
+			p[a[z]] = x
+			p[a[y]] = z
+			a[x] = a[z]
+			a[z] = a[y]
+			//a[x], a[y], a[z] = a[z], a[x], a[y]
+		}
+		if a[n-1] < a[n] { // 注意 a 从 1 开始
+			Fprintln(out, "YES")
+		} else {
+			Fprintln(out, "NO")
+		}
+	}
+}
+
+//func main() { CF1585D(os.Stdin, os.Stdout) }

main/1500-1599/1585D_test.go

@@ -0,0 +1,38 @@
+package main
+
+import (
+	"github.com/EndlessCheng/codeforces-go/main/testutil"
+	"testing"
+)
+
+// https://codeforces.com/problemset/problem/1585/D
+// https://codeforces.com/problemset/status/1585/problem/D
+func TestCF1585D(t *testing.T) {
+	// just copy from website
+	rawText := `
+inputCopy
+7
+1
+1
+2
+2 2
+2
+2 1
+3
+1 2 3
+3
+2 1 3
+3
+3 1 2
+4
+2 1 4 3
+outputCopy
+YES
+YES
+NO
+YES
+NO
+YES
+YES`
+	testutil.AssertEqualCase(t, rawText, 0, CF1585D)
+}