Solve excel-sheet-column-number.

source/excel_sheet_column_number/mod.rs

@@ -0,0 +1,18 @@
+pub fn title_to_number(title: String) -> i32 {
+  let mut result = 0;
+
+  for (index, character) in title.chars().rev().enumerate() {
+    // Convert the character to a number and subtract 9 so A will equal 1.
+    let number = character.to_digit(36).unwrap() - 9;
+
+    let n = if index == 0 {
+      number
+    } else {
+      26_u32.pow(index as u32) * number
+    };
+
+    result += n;
+  }
+
+  result as i32
+}

source/lib.rs

@@ -1,4 +1,5 @@
 pub mod add_binary;
+pub mod excel_sheet_column_number;
 pub mod implement_strstr;
 pub mod length_of_last_word;
 pub mod longest_common_prefix;

tests/excel_sheet_column_number.rs

@@ -0,0 +1,11 @@
+use leetcode::excel_sheet_column_number::title_to_number;
+
+use test_case::test_case;
+
+#[test_case("A", 1; "minimum")]
+#[test_case("FXSHRXW", i32::MAX; "maximum")]
+#[test_case("AB", 28; "double")]
+#[test_case("AZY", 1377; "triple")]
+fn test_excel_sheet_column_number(input: &str, expected: i32) {
+  assert_eq!(title_to_number(input.to_string()), expected);
+}