update: reverse sequence

Sources/Sdifft/Diff.swift

@@ -49,10 +49,10 @@ func drawMatrix(from: String, to: String) -> Matrix {
     var result: [[Int]] = Array(repeating: Array(repeating: 0, count: column), count: row)
     for i in 1..<row {
         for j in 1..<column {
-            if from[i-1] == to[j-1] {
-                result[i][j] = result[i-1][j-1] + 1
+            if from[i - 1] == to[j - 1] {
+                result[i][j] = result[i - 1][j - 1] + 1
             } else {
-                result[i][j] = max(result[i][j-1], result[i-1][j])
+                result[i][j] = max(result[i][j - 1], result[i - 1][j])
             }
         }
     }
@@ -72,11 +72,11 @@ typealias Position = (row: Int, column: Int)
 /// - Returns: same character's indexes
 func lcs(from: String, to: String, position: Position, matrix: Matrix, same: (from: [Int], to: [Int])) -> (from: [Int], to: [Int]) {
     if position.row == 0 || position.column == 0 {
-        return (same.from.reversed(), same.to.reversed())
+        return same
     }
-    if from[position.row-1] == to[position.column-1] {
+    if from[position.row - 1] == to[position.column - 1] {
         return lcs(from: from, to: to, position: (position.row - 1, position.column - 1), matrix: matrix, same: (same.from + [position.row - 1], same.to + [position.column - 1]))
-    } else if matrix[position.row-1][position.column] >= matrix[position.row][position.column-1] {
+    } else if matrix[position.row - 1][position.column] >= matrix[position.row][position.column - 1] {
         return lcs(from: from, to: to, position: (position.row - 1, position.column), matrix: matrix, same: same)
     } else {
         return lcs(from: from, to: to, position: (position.row, position.column - 1), matrix: matrix, same: same)
@@ -144,9 +144,25 @@ public struct Modification {
     public let same: [CountableClosedRange<Int>]
     public let base: Base
 
-    init(from: String, to: String, matrix: Matrix) {
-        let same =
+
+    /// Return modification with strings
+    ///
+    /// - Parameters:
+    ///   - from: string
+    ///   - to: string that be compared
+    ///   - matrix: matrix
+    ///   - isReversed: from and to is reversed
+    init(from: String, to: String, matrix: Matrix, isReversed: Bool) {
+        var same =
             lcs(from: from, to: to, position: (from.count, to.count), matrix: matrix, same: ([], []))
+
+        if isReversed {
+            same = (
+                same.from.map({ from.count - 1 - $0 }),
+                same.to.map({ to.count - 1 - $0 })
+            )
+        }
+
         add = same.to.getChangeRanges(max: to.count - 1)
         delete = same.from.getChangeRanges(max: from.count - 1)
         if add.isEmpty {
@@ -160,15 +176,15 @@ public struct Modification {
 }
 
 public struct Diff {
-    public let from: String
-    public let to: String
     public let modification: Modification
     let matrix: Matrix
 
     public init(from: String, to: String) {
-        self.from = from
-        self.to = to
-        matrix = drawMatrix(from: from, to: to)
-        modification = Modification(from: from, to: to, matrix: matrix)
+        // because LCS is 'bottom-up'
+        // so them need be reversed to get the normal sequence
+        let reversedFrom = String(from.reversed())
+        let reversedTo = String(to.reversed())
+        matrix = drawMatrix(from: reversedFrom, to: reversedTo)
+        modification = Modification(from: reversedFrom, to: reversedTo, matrix: matrix, isReversed: true)
     }
 }

Tests/SdifftTests/SdifftTests.swift

@@ -12,7 +12,7 @@ extension String {
 class DiffTests: XCTestCase {
     func testMatrix() {
         assert(
-            Diff(from: "abcd", to: "acd").matrix == [
+            drawMatrix(from: "abcd", to: "acd") == [
                 [0, 0, 0, 0],
                 [0, 1, 1, 1],
                 [0, 1, 1, 1],
@@ -22,7 +22,7 @@ class DiffTests: XCTestCase {
         )
 
         assert(
-            Diff(from: "abcdegh", to: "ae").matrix == [
+            drawMatrix(from: "abcdegh", to: "ae") == [
                 [0, 0, 0],
                 [0, 1, 1],
                 [0, 1, 1],
@@ -35,7 +35,7 @@ class DiffTests: XCTestCase {
         )
 
         assert(
-            Diff(from: "adf", to: "d").matrix == [
+            drawMatrix(from: "adf", to: "d") == [
                 [0, 0],
                 [0, 0],
                 [0, 1],
@@ -44,14 +44,14 @@ class DiffTests: XCTestCase {
         )
 
         assert(
-            Diff(from: "d", to: "adf").matrix == [
+            drawMatrix(from: "d", to: "adf") == [
                 [0, 0, 0, 0],
                 [0, 0, 1, 1]
             ]
         )
 
         assert(
-            Diff(from: "", to: "").matrix == [
+             drawMatrix(from: "", to: "") == [
                 [0],
             ]
         )
@@ -140,8 +140,8 @@ class DiffTests: XCTestCase {
         let from3 = "A\r\n\r\nB\r\n\r\nC"
         let diff3 = Diff(from: from3, to: to3)
         assert(diff3.modification.add == [])
-        assert(diff3.modification.delete == [1...1, 4...4])
-        assert(diff3.modification.same == [0...0, 2...3, 5...6])
+        assert(diff3.modification.delete == [2...2, 5...5])
+        assert(diff3.modification.same == [0...1, 3...4, 6...6])
     }
 
     func testString1() {
@@ -170,6 +170,19 @@ class DiffTests: XCTestCase {
             to[diff.modification.same[1]] == "j"
         )
     }
+
+    func testString3() {
+        let to = "A\r\nB\r\nC"
+        let from = "A\r\n\r\nB\r\n\r\nC"
+        let diff = Diff(from: from, to: to)
+        assert(
+            diff.modification.add.count == 0 &&
+            from[diff.modification.delete[0]] == "\r\n" &&
+            (diff.modification.base == .to ? to[diff.modification.same[0]]: from[diff.modification.same[0]]) == "A\r\n" &&
+            (diff.modification.base == .to ? to[diff.modification.same[1]]: from[diff.modification.same[1]]) == "B\r\n" &&
+            (diff.modification.base == .to ? to[diff.modification.same[2]]: from[diff.modification.same[2]]) == "C"
+        )
+    }
 
     func testTime() {
         // 1000 character * 1000 character: 3.681s
@@ -187,6 +200,7 @@ class DiffTests: XCTestCase {
         ("testRange", testRange),
         ("testString1", testString1),
         ("testString2", testString2),
+        ("testString3", testString3),
         ("testTime", testTime)
     ]
 }