iwilbert

public boolean isPerm(String str1, String str2) {
		// edge cases: null, len not equal, len = 0
        if(str1 == null || str2 == null)
        	return false;
        int m = str1.length();
        int n = str2.length();
        if(m != n)
        	return false;
        if(m == 0)
        	return true;

iwilbert

public void replace(char[] line) {
		int len;					// original length;
		int cnt = 0;				// space count
		for(len = 0; line[len] != '\0'; len++)
		{
			if(line[len] == ' ')
				cnt++;
		}
		int new_len = len + cnt*2;	// length of new string
		int k = new_len - 1;		// starts from the end of new string

iwilbert

public String compress(String line) {
		// corner cases: null, 0-length
		if(line == null || line.length() == 0)
			return "";
		int len = line.length();
		char prev = line.charAt(0);			// save the previous character
		int cnt = 1;
		StringBuffer sb = new StringBuffer();
		for(int i = 1; i < len; i++) {
			if(line.charAt(i) == prev)		// if current == previous

iwilbert

public void rotate(int[][] matrix) {
		if(matrix == null)
			return;
		int N = matrix.length;
		for(int i = 0; i < N/2; i++)					// This is the layer
			for(int j = i; j < N-i-1; j++) {			// This is the offset to start
				// swap
				int t = matrix[i][j];
				matrix[i][j] = matrix[N-j-1][i];
				matrix[N-j-1][i] = matrix[N-i-1][N-j-1];

iwilbert

public void zero(int[][] matrix) {
		if(matrix == null)
			return;
		int m = matrix.length;
		if(m == 0)
			return;
		int n = matrix[0].length;
		boolean[] row_zero = new boolean[m];
		boolean[] col_zero = new boolean[n];
		for(int i = 0; i < m; i++)

iwilbert

    public boolean isRotate(String s1, String s2) {
        if(s1 == null || s2 == null || s1.isEmpty() || s2.isEmpty() || s1.length() != s2.length())
            return false;
        else
            return isSubstring(s1+s1, s2);
    }
    
    private boolean isSubstring(String s1, String s2) {
        return s1.contains(s2);
    }

iwilbert

    // O(N)
    public void removeDuplicate(ListNode head) {
        if(head == null || head.next == null) {
            return;
        }
        HashMap<Integer, Integer> dict = new HashMap<Integer, Integer>();
        ListNode cur = head;
        ListNode prev = head;
        while(cur != null) {
            if(!dict.containsKey(cur.val)) {

iwilbert

public int kthToLast(ListNode head, int k) {
        if(head == null)
            return -1;
        ListNode p1, p2;
        p1 = p2 = head;
        for(int i = 0; p1 != null && i < k; i++) {
            p1 = p1.next;
        }
        while(p1 != null) {
            p1 = p1.next;

iwilbert

public void deleteNode(ListNode node) {
        // node is null or node is the last node
        if(node == null || node.next == null)
            return;
        ListNode next = node.next;
        node.val = next.val;
        node.next = next.next;
        next = null;
    }

iwilbert

    public ListNode partition(ListNode head, int x) {
        if(head == null || head.next == null)
            return head;
        ListNode lessHead, nolessHead, lessCur, nolessCur;
        lessHead = nolessHead = lessCur = nolessCur = null;
        ListNode cur, next;
        cur = head;
        while(cur != null) {
            next = cur.next;
            cur.next = null;        // cut off cur node from the list