leetcode

commit a938639a498879a8078db75a3e1ad060e574a021
parent d17fc79d3731489167a983ead40b150499cbd415
Author: Jack Sangdahl <jack@pngu.org>
Date:   Fri,  3 Apr 2026 20:42:10 -0600

2075. decode the slanted ciphertext

Diffstat:
A
decode_slanted_ciphertext.c
 | 
46
++++++++++++++++++++++++++++++++++++++++++++++
A
decode_slanted_ciphertext.py
 | 
30
++++++++++++++++++++++++++++++

2 files changed, 76 insertions(+), 0 deletions(-)
diff --git a/decode_slanted_ciphertext.c b/decode_slanted_ciphertext.c
@@ -0,0 +1,46 @@
+// 2075. Decode the Slanted Ciphertext
+#include "leetcode.h"
+
+/*
+ * a string 'originalText' is encoded using a slanted transposition cipher to a
+ * string 'encodedText' with the help of a matrix having a fixed number of
+ * 'rows'. given the encoded string 'encodedText' and a numbe of rows, return
+ * the original string 'originalText'.
+ */
+
+char *decodeCiphertext(char *encodedText, int rows) {
+  if (rows == 1)
+    return strdup(encodedText);
+  int n = strlen(encodedText), cols = n / rows, idx = 0;
+  char *ans = (char *)malloc((n + 1) * sizeof(char));
+  for (int c = 0; c < cols; c++) {
+    int r = 0, j = c;
+    while (r < rows && j < cols) {
+      ans[idx++] = encodedText[r * cols + j];
+      r++;
+      j++;
+    }
+  }
+  while (idx > 0 && ans[idx - 1] == ' ')
+    idx--;
+  ans[idx] = '\0';
+  return ans;
+}
+
+int main() {
+  char *et1 = "ch   ie   pr";
+  char *et2 = "iveo    eed   l te   olc";
+  char *et3 = "coding";
+  char *dc1 = decodeCiphertext(et1, 3);
+  char *dc2 = decodeCiphertext(et2, 4);
+  char *dc3 = decodeCiphertext(et3, 1);
+  printf("%s\n", dc1);
+  assert(!strcmp(dc1, "cipher"));
+  printf("%s\n", dc2);
+  assert(!strcmp(dc2, "i love leetcode"));
+  printf("%s\n", dc3);
+  assert(!strcmp(dc3, "coding"));
+  free(dc1);
+  free(dc2);
+  free(dc3);
+}
diff --git a/decode_slanted_ciphertext.py b/decode_slanted_ciphertext.py
@@ -0,0 +1,30 @@
+# 2075. Decode the Slanted Ciphertext
+
+"""
+a string 'originalText' is encoded using a slanted transposition cipher to a
+string 'encodedText' with the help of a matrix having a fixed number of
+'rows'. given the encoded string 'encodedText' and a numbe of rows, return
+the original string 'originalText'.
+"""
+
+
+class Solution:
+    def decodeCiphertext(self, encodedText: str, rows: int) -> str:
+        if rows == 1:
+            return encodedText
+        n, ans = len(encodedText), []
+        cols = n // rows
+        for c in range(cols):
+            r, j = 0, c
+            while r < rows and j < cols:
+                ans.append(encodedText[r * cols + j])
+                r += 1
+                j += 1
+        return "".join(ans).rstrip()
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    print(obj.decodeCiphertext(encodedText="ch   ie   pr", rows=3))
+    print(obj.decodeCiphertext(encodedText="iveo    eed   l te   olc", rows=4))
+    print(obj.decodeCiphertext(encodedText="coding", rows=1))