484. Find Permutation

By now, you are given a secret signature consisting of character 'D' and 'I'. 'D' represents a decreasing relationship between two numbers, 'I' represents an increasing relationship between two numbers. And our secret signature was constructed by a special integer array, which contains uniquely all the different number from 1 to n (n is the length of the secret signature plus 1). For example, the secret signature "DI" can be constructed by array [2,1,3] or [3,1,2], but won't be constructed by array [3,2,4] or [2,1,3,4], which are both illegal constructing special string that can't represent the "DI" secret signature.

On the other hand, now your job is to find the lexicographically smallest permutation of [1, 2, ... n] could refer to the given secret signature in the input.

Example 1:

Input: "I"
Output: [1,2]
Explanation: [1,2] is the only legal initial spectial string can construct secret signature "I", where the number 1 and 2 construct an increasing relationship.

Example 2:

Input: "DI"
Output: [2,1,3]
Explanation: Both [2,1,3] and [3,1,2] can construct the secret signature "DI", 
but since we want to find the one with the smallest lexicographical permutation, you need to output [2,1,3]

Note:

  • The input string will only contain the character 'D' and 'I'.
  • The length of input string is a positive integer and will not exceed 10,000
  • Rust Solution

    struct Solution;
    
    impl Solution {
        fn find_permutation(s: String) -> Vec<i32> {
            let n = s.len();
            let mut res: Vec<i32> = (1..=(n + 1) as i32).collect();
            let s: Vec<char> = s.chars().collect();
            let mut l = 0;
            while l < n {
                if s[l] == 'D' {
                    let mut r = l;
                    while r < n && s[r] == 'D' {
                        r += 1;
                    }
                    res[l..=r].reverse();
                    l = r;
                } else {
                    l += 1;
                }
            }
            res
        }
    }
    
    #[test]
    fn test() {
        let s = "I".to_string();
        let res = vec![1, 2];
        assert_eq!(Solution::find_permutation(s), res);
        let s = "DI".to_string();
        let res = vec![2, 1, 3];
        assert_eq!(Solution::find_permutation(s), res);
    }
    

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