add new solutions

solutions/36/q3666/solution.go

@@ -0,0 +1,71 @@
+// Package q3666 implements a solution for https://leetcode.com/problems/minimum-operations-to-equalize-binary-string/
+package q3666
+
+import (
+	"strings"
+
+	rbt "github.com/emirpasic/gods/v2/trees/redblacktree"
+)
+
+type void struct{}
+
+const INF = 1<<63 - 1
+
+var (
+	qBuf    = make([]int, 0, 1e5+1)
+	nOpsBuf = make([]int, 0, 1e5+1)
+)
+
+func minOperations(s string, k int) int {
+	zeros := strings.Count(s, "0")
+	length := len(s)
+
+	if zeros%2 == 1 && k%2 == 0 {
+		return -1
+	}
+	if k == length && zeros != 0 && zeros != length {
+		return -1
+	}
+	if zeros%k == 0 {
+		return zeros / k
+	}
+
+	nOps := nOpsBuf[:length+1]
+	sets := [2]*rbt.Tree[int, void]{
+		rbt.New[int, void](), rbt.New[int, void](),
+	}
+	for i := range length + 1 {
+		sets[i%2].Put(i, void{})
+		nOps[i] = INF
+	}
+
+	nOps[zeros] = 0
+	sets[zeros%2].Remove(zeros)
+	queue := qBuf[:0]
+	queue = append(queue, zeros)
+
+	for ; len(queue) > 0; queue = queue[1:] {
+		z := queue[0]
+		par := (z + k) % 2
+
+		minFlipZ := max(k-(length-z), 0)
+		maxFlipZ := min(k, z)
+		minNewZ := z + k - 2*maxFlipZ
+		maxNewZ := z + k - 2*minFlipZ
+
+		next, found := sets[par].Ceiling(minNewZ)
+		for ; found && next.Key <= maxNewZ; next, found = sets[par].Ceiling(minNewZ) {
+			nextZ := next.Key
+			sets[par].Remove(nextZ)
+
+			nOps[nextZ] = nOps[z] + 1
+			if nextZ%k == 0 {
+				return nOps[nextZ] + nextZ/k
+			}
+			queue = append(queue, nextZ)
+		}
+	}
+	return -1
+}
+
+var _ = minOperations