Implemented edit distance dp function (#20)

Author: spirosmaggioros

build.zig

@@ -104,6 +104,13 @@ pub fn build(b: *std.Build) void {
             .name = "longestIncreasingSubsequence.zig",
             .category = "dynamicProgramming"
         });
+    if (std.mem.eql(u8, op, "dp/editDistance"))
+        build_algorithm(b, .{
+            .optimize = optimize,
+            .target = target,
+            .name = "editDistance.zig",
+            .category = "dynamicProgramming"
+        });
 
     // Math algorithms
     if (std.mem.eql(u8, op, "math/ceil"))

dynamicProgramming/editDistance.zig

@@ -0,0 +1,76 @@
+const std = @import("std");
+const testing = std.testing;
+
+// Function that computes the minimum distance(or operations) to make 2 strings equal
+// Well known as the edit distance dp function.
+// Arguments:
+//      word1: The first passed string
+//      word2: The second passed string
+// Returns u32: The minimum operations to make the 2 strings equal
+pub fn minDist(comptime word1: []const u8, comptime word2: []const u8) u32 {
+    if (word1.len == 0 and word2.len == 0) {
+        return 0;
+    }
+    if (word1.len == 0 and word2.len != 0) {
+        return @as(u32, @intCast(word2.len));
+    }
+    if (word1.len != 0 and word2.len == 0) {
+        return @as(u32, @intCast(word1.len));
+    }
+
+    const n: usize = word1.len;
+    const w: usize = word2.len;
+
+    var dp: [n + 1][w + 1]u32 = undefined;
+    for (0..(n + 1)) |i| {
+        dp[i][0] = @as(u32, @intCast(i));
+    }
+
+    for (0..(w + 1)) |i| {
+        dp[0][i] = @as(u32, @intCast(i));
+    }
+
+    for (1..(n + 1)) |i| {
+        for (1..(w + 1)) |j| {
+            if (word1[i - 1] == word2[j - 1]) {
+                dp[i][j] = dp[i - 1][j - 1];
+            } else {
+                dp[i][j] = @min(dp[i - 1][j - 1], @min(dp[i - 1][j], dp[i][j - 1])) + 1;
+            }
+        }
+    }
+
+    return dp[n][w];
+}
+
+test "Testing edit distance function" {
+    const word1 = "hello";
+    const word2 = "world";
+
+    try testing.expect(minDist(word1, word2) == 4);
+
+    const word3 = "Hell0There";
+    const word4 = "hellothere";
+
+    try testing.expect(minDist(word3, word4) == 3);
+
+    const word5 = "abcdefg";
+    const word6 = "abcdefg";
+
+    try testing.expect(minDist(word5, word6) == 0);
+
+    const word7 = "";
+    const word8 = "abasda";
+
+    try testing.expect(minDist(word7, word8) == 6);
+
+    const word9 = "abcsa";
+    const word10 = "";
+
+    try testing.expect(minDist(word9, word10) == 5);
+
+    const word11 = "sdasdafda";
+    const word12 = "sdasdbbba";
+
+    try testing.expect(minDist(word11, word12) == 3);
+}

runall.cmd

@@ -26,6 +26,7 @@ rem Dynamic Programming
 %ZIG_TEST% -Dalgorithm=dp/coinChange %Args%
 %ZIG_TEST% -Dalgorithm=dp/knapsack %Args%
 %ZIG_TEST% -Dalgorithm=dp/longestIncreasingSubsequence %Args%
+%ZIG_TEST% -Dalgorithm=dp/editDistance %Args%
 
 rem Sort
 %ZIG_TEST% -Dalgorithm=sort/quicksort %Args%

runall.sh

@@ -26,6 +26,7 @@ $ZIG_TEST -Dalgorithm=ds/lrucache $Args
 $ZIG_TEST -Dalgorithm=dp/coinChange $Args
 $ZIG_TEST -Dalgorithm=dp/knapsack $Args
 $ZIG_TEST -Dalgorithm=dp/longestIncreasingSubsequence $Args
+$ZIG_TEST -Dalgorithm=dp/editDistance $Args
 
 ## Sort
 $ZIG_TEST -Dalgorithm=sort/quicksort $Args