243. Shortest Word Distance

Given a list of words and two words word1 and word2, return the shortest distance between these two words in the list.

Example:
Assume that words = ["practice", "makes", "perfect", "coding", "makes"].

Input: word1 = “coding”, word2 = “practice”
Output: 3

Input: word1 = "makes", word2 = "coding"
Output: 1

Note:
You may assume that word1 does not equal to word2, and word1 and word2 are both in the list.

在brute force的基础上改进：

用两个index分别存word1, word2的most recent locations，每次如果有某一个word出现在新位置，只要与另一个word最近出现的位置求距离即可

time: O(n), space: O(1)

class Solution {
    public int shortestDistance(String[] words, String word1, String word2) {
        int minDist = words.length;
        int idx1 = -1, idx2 = -1;
        for(int i = 0; i < words.length; i++) {
            if(word1.equals(words[i])) {
                idx1 = i;
            } else if(word2.equals(words[i])) {
                idx2 = i;
            }
            
            if(idx1 != -1 && idx2 != -1) {
                minDist = Math.min(minDist, Math.abs(idx1 - idx2));
            }
        }
        return minDist;
    }
}