A-M baby

Task/Longest-common-subsequence/Go/longest-common-subsequence-1.go

@@ -0,0 +1,15 @@
+func lcs(a, b string) string {
+    aLen := len(a)
+    bLen := len(b)
+    if aLen == 0 || bLen == 0 {
+        return ""
+    } else if a[aLen-1] == b[bLen-1] {
+        return lcs(a[:aLen-1], b[:bLen-1]) + string(a[aLen-1])
+    }
+    x := lcs(a, b[:bLen-1])
+    y := lcs(a[:aLen-1], b)
+    if len(x) > len(y) {
+        return x
+    }
+    return y
+}

Task/Longest-common-subsequence/Go/longest-common-subsequence-2.go

@@ -0,0 +1,41 @@
+func lcs(a, b string) string {
+    aLen := len(a)
+    bLen := len(b)
+    lengths := make([][]int, aLen+1)
+    for i := 0; i <= aLen; i++ {
+        lengths[i] = make([]int, bLen+1)
+    }
+    // row 0 and column 0 are initialized to 0 already
+
+    for i := 0; i < aLen; i++ {
+        for j := 0; j < bLen; j++ {
+            if a[i] == b[j] {
+                lengths[i+1][j+1] = lengths[i][j]+1
+            } else if lengths[i+1][j] > lengths[i][j+1] {
+                lengths[i+1][j+1] = lengths[i+1][j]
+            } else {
+                lengths[i+1][j+1] = lengths[i][j+1]
+            }
+        }
+    }
+
+    // read the substring out from the matrix
+    s := make([]byte, 0, lengths[aLen][bLen])
+    for x, y := aLen, bLen; x != 0 && y != 0; {
+        if lengths[x][y] == lengths[x-1][y] {
+            x--
+        } else if lengths[x][y] == lengths[x][y-1] {
+            y--
+        } else {
+            s = append(s, a[x-1])
+            x--
+            y--
+        }
+    }
+    // reverse string
+    r := make([]byte, len(s))
+    for i := 0; i < len(s); i++ {
+        r[i] = s[len(s)-1-i]
+    }
+    return string(r)
+}