2515. Shortest Distance to Target String in a Circular Array

Description

You are given a 0-indexed circular string array words and a string target. A circular array means that the array's end connects to the array's beginning.

• Formally, the next element of words[i] is words[(i + 1) % n] and the previous element of words[i] is words[(i - 1 + n) % n], where n is the length of words.

Starting from startIndex, you can move to either the next word or the previous word with 1 step at a time.

Return the shortest distance needed to reach the string target. If the string target does not exist in words, return -1.

 

Example 1:

Input: words = ["hello","i","am","leetcode","hello"], target = "hello", startIndex = 1
Output: 1
Explanation: We start from index 1 and can reach "hello" by
- moving 3 units to the right to reach index 4.
- moving 2 units to the left to reach index 4.
- moving 4 units to the right to reach index 0.
- moving 1 unit to the left to reach index 0.
The shortest distance to reach "hello" is 1.

Example 2:

Input: words = ["a","b","leetcode"], target = "leetcode", startIndex = 0
Output: 1
Explanation: We start from index 0 and can reach "leetcode" by
- moving 2 units to the right to reach index 2.
- moving 1 unit to the left to reach index 2.
The shortest distance to reach "leetcode" is 1.

Example 3:

Input: words = ["i","eat","leetcode"], target = "ate", startIndex = 0
Output: -1
Explanation: Since "ate" does not exist in words, we return -1.

 

Constraints:

• 1 <= words.length <= 100
• 1 <= words[i].length <= 100
• words[i] and target consist of only lowercase English letters.
• 0 <= startIndex < words.length

 

Solutions

Solution: Greedy

• Time complexity: O(n)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {string[]} words
 * @param {string} target
 * @param {number} startIndex
 * @return {number}
 */
const closestTarget = function (words, target, startIndex) {
  const n = words.length;
  let result = Number.MAX_SAFE_INTEGER;

  for (let index = 0; index < n; index++) {
    const word = words[index];

    if (word !== target) continue;

    const leftSteps = (startIndex - index + n) % n;
    const rightSteps = (index - startIndex + n) % n;

    result = Math.min(leftSteps, rightSteps, result);
  }

  return result === Number.MAX_SAFE_INTEGER ? -1 : result;
};