[2000][1A] CF629C DP

main/600-699/629C.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"bufio"
+	. "fmt"
+	"io"
+)
+
+// github.com/EndlessCheng/codeforces-go
+func CF629C(_r io.Reader, out io.Writer) {
+	in := bufio.NewReader(_r)
+	const mod = 1e9 + 7
+
+	var n, m, sum, min int
+	var s []byte
+	Fscan(in, &n, &m, &s)
+	for _, b := range s {
+		if b == '(' {
+			sum++
+		} else {
+			if sum--; sum < min {
+				min = sum
+			}
+		}
+	}
+	d := n - m
+	if d+min < 0 {
+		Fprint(out, 0)
+		return
+	}
+
+	dp := make([][]int, d+1)
+	for i := range dp {
+		dp[i] = make([]int, d+1)
+	}
+	dp[0][0] = 1
+	for i := 1; i <= d; i++ {
+		for j := 0; j <= d; j++ {
+			if j > 0 {
+				dp[i][j] = dp[i-1][j-1]
+			}
+			if j < d {
+				dp[i][j] = (dp[i][j] + dp[i-1][j+1]) % mod
+			}
+		}
+	}
+
+	ans := int64(0)
+	for i, dv := range dp {
+		for j := -min; j <= d && j+sum <= d; j++ {
+			ans = (ans + int64(dv[j])*int64(dp[d-i][j+sum])) % mod
+		}
+	}
+	Fprint(out, ans)
+}
+
+//func main() { CF629C(os.Stdin, os.Stdout) }

main/600-699/629C_test.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"github.com/EndlessCheng/codeforces-go/main/testutil"
+	"testing"
+)
+
+// https://codeforces.com/problemset/problem/629/C
+// https://codeforces.com/problemset/status/629/problem/C
+func TestCF629C(t *testing.T) {
+	// just copy from website
+	rawText := `
+inputCopy
+4 1
+(
+outputCopy
+4
+inputCopy
+4 4
+(())
+outputCopy
+1
+inputCopy
+4 3
+(((
+outputCopy
+0`
+	testutil.AssertEqualCase(t, rawText, 0, CF629C)
+}