add new solutions

solutions/19/q1980/solution.go

@@ -0,0 +1,37 @@
+// Package q1980 implements a solution for https://leetcode.com/problems/find-unique-binary-string/
+package q1980
+
+import "slices"
+
+func toNumber(s string) int {
+	ret := 0
+	for i := range len(s) {
+		ret = ret<<1 + int(s[i]-'0')
+	}
+	return ret
+}
+
+func fromNumber(n, length int) string {
+	buf := make([]byte, length)
+	for i := range length {
+		buf[i] = byte(n&1) + '0'
+		n >>= 1
+	}
+	slices.Reverse(buf)
+	return string(buf)
+}
+
+func findDifferentBinaryString(nums []string) string {
+	slices.Sort(nums)
+	last := -1
+	for i := range nums {
+		num := toNumber(nums[i])
+		if num > last+1 {
+			break
+		}
+		last = num
+	}
+	return fromNumber(last+1, len(nums[0]))
+}
+
+var _ = findDifferentBinaryString