670. Maximum Swap

Author: Partho Biswas

leetcode.com/swift/DS_ALGO_PRAC.playground/Contents.swift

@@ -1,30 +1,2 @@
 import Foundation
-class Solution {
-    func maximumSwap(_ num: Int) -> Int {
-        var digits: [Int] = String(num).compactMap{ $0.wholeNumberValue }
-        print("Digits: \(digits)")
-        let sortedDigits: [Int] = digits.sorted {$0 > $1}
-        print("Sorted: \(sortedDigits)")
-        var numIdxMap = [Int:Int]()
-        for (idx, item) in digits.enumerated() {
-            numIdxMap[item] = idx
-        }
-        var swapIdx = 0
-        while swapIdx < digits.count {
-            if digits[swapIdx] != sortedDigits[swapIdx] {
-                let targetIdx = numIdxMap[sortedDigits[swapIdx]]!
-                print("targetIdx: \(targetIdx), swapIdx: \(targetIdx)")
-                digits.swapAt(targetIdx, targetIdx)
-//                (digits[swapIdx], digits[swapIdx]) = (digits[targetIdx], digits[swapIdx])
-                break
-            }
-        }
-        print("Digits: \(digits)")
-        return Int(digits.reduce("") { $0 + String($1) }) ?? num
-    }
-}
 
-/*
- 
- 12345678
- */

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/670_Maximum_Swap.swift

@@ -3,9 +3,7 @@ import Foundation
 class Solution {
     func maximumSwap(_ num: Int) -> Int {
         var digits: [Int] = String(num).compactMap{ $0.wholeNumberValue }
-        print("Digits: \(digits)")
         let sortedDigits: [Int] = digits.sorted {$0 > $1}
-        print("Sorted: \(sortedDigits)")
         var numIdxMap = [Int:Int]()
         for (idx, item) in digits.enumerated() {
             numIdxMap[item] = idx
@@ -14,7 +12,6 @@ class Solution {
         while swapIdx < digits.count {
             if digits[swapIdx] != sortedDigits[swapIdx] {
                 let targetIdx = numIdxMap[sortedDigits[swapIdx]]!
-                print("targetIdx: \(targetIdx), swapIdx: \(swapIdx)")
                 digits.swapAt(targetIdx, swapIdx)
                 break
             }
@@ -23,3 +20,27 @@ class Solution {
         return Int(digits.reduce("") { $0 + String($1) }) ?? num
     }
 }
+
+
+
+import Foundation
+// Time: O(n)
+class Solution {
+    func maximumSwap(_ num: Int) -> Int {
+        var digits: [Int] = String(num).compactMap{ $0.wholeNumberValue }
+        var numIdxMap = [Int:Int]()
+        for (idx, item) in digits.enumerated() {
+            numIdxMap[item] = idx
+        }
+        
+        for currentIdx in 0..<digits.count {
+            for numToSwapWith in stride(from: 9, to: digits[currentIdx], by: -1) {
+                if let targetIdx = numIdxMap[numToSwapWith], targetIdx > currentIdx {
+                    digits.swapAt(currentIdx, targetIdx)
+                    return Int(digits.reduce("") { $0 + String($1) }) ?? num
+                }
+            }
+        }
+        return num
+    }
+}