diff --git a/solved/LeetCode/Challenges/2020/January/23.kt b/solved/LeetCode/Challenges/2020/January/23.kt
new file mode 100644
index 00000000..86bd7a7f
--- /dev/null
+++ b/solved/LeetCode/Challenges/2020/January/23.kt
@@ -0,0 +1,34 @@
+class Solution {
+  fun diagonalSort(mat: Array<IntArray>): Array<IntArray> {
+    val rows = mat.size
+    val cols = mat[0].size
+    
+    fun fix(stI: Int, stJ: Int) {
+      var i = stI;
+      var j = stJ;
+      var nums = ArrayDeque<Int>()
+      while (i < rows && j < cols) {
+        nums.addLast(mat[i][j])
+        i++
+        j++
+      }
+      val s = ArrayDeque(nums.sorted())
+
+      j = stJ;
+      i = stI;
+      while (i < rows && j < cols) {
+        mat[i][j] = s.removeFirst()
+        i++
+        j++
+      }
+    }
+    
+    for (i in 0 until rows) {
+      fix(i, 0)
+    }
+    for (i in 1 until cols) {
+      fix(0, i)
+    }
+    return mat
+  }
+}