944. Delete Columns to Make Sorted

You are given an array of n strings strs, all of the same length.

The strings can be arranged such that there is one on each line, making a grid. For example, strs = ["abc", "bce", "cae"] can be arranged as:

abc
bce
cae

You want to delete the columns that are not sorted lexicographically. In the above example (0-indexed), columns 0 ('a', 'b', 'c') and 2 ('c', 'e', 'e') are sorted while column 1 ('b', 'c', 'a') is not, so you would delete column 1.

Return the number of columns that you will delete.

 

Example 1:

Input: strs = ["cba","daf","ghi"]
Output: 1
Explanation: The grid looks as follows:
  cba
  daf
  ghi
Columns 0 and 2 are sorted, but column 1 is not, so you only need to delete 1 column.

Example 2:

Input: strs = ["a","b"]
Output: 0
Explanation: The grid looks as follows:
  a
  b
Column 0 is the only column and is sorted, so you will not delete any columns.

Example 3:

Input: strs = ["zyx","wvu","tsr"]
Output: 3
Explanation: The grid looks as follows:
  zyx
  wvu
  tsr
All 3 columns are not sorted, so you will delete all 3.

 

Constraints:

  • n == strs.length
  • 1 <= n <= 100
  • 1 <= strs[i].length <= 1000
  • strs[i] consists of lowercase English letters.

Rust Solution

struct Solution;

impl Solution {
    fn min_deletion_size(a: Vec<String>) -> i32 {
        let mut d = 0;
        let a: Vec<&[u8]> = a.iter().map(|s| s.as_bytes()).collect();
        let n = a.len();
        let m = a[0].len();
        for i in 0..m {
            for j in 1..n {
                if a[j][i] < a[j - 1][i] {
                    d += 1;
                    break;
                }
            }
        }
        d
    }
}

#[test]
fn test() {
    let a: Vec<String> = vec_string!["cba", "daf", "ghi"];
    assert_eq!(Solution::min_deletion_size(a), 1);
    let a: Vec<String> = vec_string!["a", "b"];
    assert_eq!(Solution::min_deletion_size(a), 0);
    let a: Vec<String> = vec_string!["zyx", "wvu", "tsr"];
    assert_eq!(Solution::min_deletion_size(a), 3);
}

Having problems with this solution? Click here to submit an issue on github.