add: leetcode 0859 solution

leetcode/0859.Buddy-Strings/859.Buddy Strings.go

@@ -0,0 +1,30 @@
+package leetcode
+
+func buddyStrings(s string, goal string) bool {
+	if len(s) != len(goal) || len(s) <= 1 {
+		return false
+	}
+	mp := make(map[byte]int)
+	if s == goal {
+		for i := 0; i < len(s); i++ {
+			if _, ok := mp[s[i]]; ok {
+				return true
+			}
+			mp[s[i]]++
+		}
+		return false
+	}
+	first, second := -1, -1
+	for i := 0; i < len(s); i++ {
+		if s[i] != goal[i] {
+			if first == -1 {
+				first = i
+			} else if second == -1 {
+				second = i
+			} else {
+				return false
+			}
+		}
+	}
+	return second != -1 && s[first] == goal[second] && s[second] == goal[first]
+}