LCS

src/lcs.rs

@@ -1,22 +1,21 @@
 use std::cmp::max;
 use std::str::Chars;
+
 use crate::matrix::Matrix;
 
 pub fn diff(a: &str, b: &str) {
     let m = build_matrix(a, b);
-    print_diff(m, &mut a.chars(), &mut b.chars(), a.len() - 1, b.len() - 1);
+    print_diff(m, a, b, a.len() - 1, b.len() - 1);
 }
 
 fn build_matrix(a: &str, b: &str) -> Matrix<i32> {
-    let mut a = a.chars();
-    let mut b = b.chars();
-    let mut m = Matrix::new(*(&a.count()), *(&b.count()), 0i32);
+    let mut m = Matrix::new(a.len(), b.len(), 0i32);
 
-    for i in 0..a.count() {
-        for j in 0..b.count() {
-            let x = a.nth(i).unwrap();
-            let y = b.nth(j).unwrap();
+    let mut i = 0;
+    let mut j = 0;
 
+    for x in a.chars() {
+        for y in b.chars() {
             let v = if x == y {
                 if i == 0 || j == 0 {
                     0
@@ -30,45 +29,79 @@ fn build_matrix(a: &str, b: &str) -> Matrix<i32> {
             };
 
             m.set(v, i, j).unwrap();
+
+            j += 1;
         }
+
+        i += 1;
+        j = 0;
     }
 
     m
 }
 
-fn print_diff(m: Matrix<i32>, a: &mut Chars, b: &mut Chars, i: usize, j: usize) {
-    if i < 0 && j < 0 {
-        println!();
-        return;
-    }
+fn print_diff(m: Matrix<i32>, a: &str, b: &str, i: usize, j: usize) {
+    let char_i = a.chars().nth(i).unwrap();
+    let char_j = b.chars().nth(j).unwrap();
 
-    let char_i = a.nth(i).unwrap();
-    let char_j = b.nth(j).unwrap();
-
-    if i < 0 {
-        print_diff(m, a, b, i, j - 1);
-        println!("+ {char_i}");
-        return;
-    }
-
-    if j < 0 {
-        print_diff(m, a, b, i - 1, j);
-        println!("- {char_j}");
-        return;
-    }
+    println!("A: {char_i}, B: {char_j}");
 
     if char_i == char_j {
-        print_diff(m, a, b, i - 1, j - 1);
         println!("  {char_i}");
         return;
     }
 
-    if m.get(i, j - 1).unwrap() >= m.get(i - 1, j).unwrap() {
-        print_diff(m, a, b, i, j - 1);
-        println!("+ {char_j}");
+    if i > 0 {
+        let up = m.get(i - 1, j).unwrap();
+
+        if j > 0 && m.get(i, j - 1).unwrap() >= up {
+            println!("+ {char_i}");
             return;
         }
+    }
 
-    print_diff(m, a, b, i - 1, j);
     println!("- {char_i}");
 }
+
+// fn print_diff(m: Matrix<i32>, a: &str, b: &str, i: usize, j: usize) {
+//     // if i < 0 && j < 0 {
+//     //     println!();
+//     //     return;
+//     // }
+//
+//     let char_i = a.chars().nth(i).unwrap();
+//     let char_j = b.chars().nth(j).unwrap();
+//
+//     // if i < 0 {
+//     //     print_diff(m, a, b, i, j - 1);
+//     //     println!("+ {char_i}");
+//     //     return;
+//     // }
+//     //
+//     // if j < 0 {
+//     //     print_diff(m, a, b, i - 1, j);
+//     //     println!("- {char_j}");
+//     //     return;
+//     // }
+//
+//     if char_i == char_j {
+//         if i > 0 && j > 0 {
+//             print_diff(m, a, b, i - 1, j - 1);
+//         }
+//
+//         println!("  {char_i}");
+//         return;
+//     }
+//
+//     if i > 0 && j > 0 && m.get(i, j - 1).unwrap() >= m.get(i - 1, j).unwrap() {
+//         print_diff(m, a, b, i, j - 1);
+//         println!("+ {char_j}");
+//         return;
+//     }
+//
+//     if i > 0 {
+//         print_diff(m, a, b, i - 1, j);
+//     }
+//
+//     println!("- {char_i}");
+// }

src/main.rs

@@ -4,9 +4,57 @@ mod matrix;
 mod lcs;
 
 fn main() {
-    let a = "let a = \"ABCDE\";";
-    let b = "let b = \"ABCDE\";";
+    let a = "abcd";
+    let b = "abce";
 
-    diff(a, b);
+    // diff(a, b);
+    lcs(a, b);
 }
 
+fn lcs(a: &str, b: &str) {
+    let n = a.len();
+    let m = b.len();
+    let max = (n + m) / 2;
+    let mut v = vec![0usize; max * 2];
+
+    for d in 0..max {
+        let mut k = 0usize;
+        while k <= d * 2 {
+            let mut x = if k == 0 || k != d * 2 && v[k - 1] < v[k + 1] {
+                v[k + 1]
+            } else {
+                v[k - 1] + 1
+            };
+
+            let mut y = if k < x {
+                x - k
+            } else {
+                0
+            };
+
+            while x < n && y < m {
+                let ac = a.chars().nth(x + 1).unwrap();
+                let bc = b.chars().nth(y + 1).unwrap();
+
+                if ac != bc {
+                    break;
+                }
+
+                x = x + 1;
+                y = y + 1;
+            }
+
+            v[k] = x;
+            if x >= n && y >= m {
+                println!("Length of a SES is D ({d})");
+                dbg!(v);
+                return;
+            }
+
+            k += 2;
+        }
+    }
+
+    println!("Length of a SES is greater than MAX ({max})");
+    dbg!(v);
+}