Shortest Word Distance

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

For example, Assume that words = ["practice", "makes", "perfect", "coding", "makes"].

Given word1 = “coding”, word2 = “practice”, return 3. Given word1 = "makes", word2 = "coding", return 1.

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

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

Move Zeroes

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Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

For example, given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0]. Note: You must do this in-place without making a copy of the array. Minimize the total number of operations.

Note: zero's order is not important at allllll!

public void moveZeroes(int[] nums) {
    int insertPt = 0;
    for (int num: nums) {
        if (num != 0) {
            nums[insertPt++] = num;
        }
    }
    for (int i = insertPt; i < nums.length; ++i) {
        nums[i] = 0;
    }
}

Meeting Rooms

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Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), determine if a person could attend all meetings.

For example, Given [[0, 30],[5, 10],[15, 20]], return false.

public boolean canAttendMeetings(Interval[] intervals) {
    Arrays.sort(intervals, (Interval i1, Interval i2) -> i1.end - i2.end);
    for (int i = 1; i < intervals.length; ++i) {
        if (intervals[i].start < intervals[i-1].end) return false;
    }
    return true;
}

Summary Ranges

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Given a sorted integer array without duplicates, return the summary of its ranges.

For example, given [0,1,2,4,5,7], return ["0->2","4->5","7"].

Harder when you loop, easily make it too complicated...

public List<String> summaryRanges(int[] nums) {
    List<String> res = new ArrayList<>();
    if (nums == null || nums.length == 0) return res;
    for(int i = 0; i < nums.length; ++i) {
        int begin = i;
        while (i + 1 < nums.length && nums[i+1] == nums[i] + 1) ++i;
        if (i == begin) res.add(String.valueOf(nums[begin]));
        else res.add(nums[begin] + "->" + nums[i]);
    }
    return res;
}