Some Code

Author: mengli

Candy.java

@@ -0,0 +1,38 @@
+There are N children standing in a line. Each child is assigned a rating value.
+
+You are giving candies to these children subjected to the following requirements:
+
+    Each child must have at least one candy.
+    Children with a higher rating get more candies than their neighbors.
+	
+What is the minimum candies you must give?
+
+public class Solution {
+    public int candy(int[] ratings) {
+        int[] A = new int[ratings.length];
+        for (int i = 0; i < A.length; i++) {
+        	A[i] = 1;
+        }
+        for (int j = 1; j < A.length; j++) {
+        	check(A, ratings, j);
+        }
+        int sum = 0;
+        for (int k = 0; k < A.length; k++) {
+        	sum += A[k];
+        }
+        return sum;
+    }
+	
+	private void check(int[] plan, int[] ratings, int start) {
+		while (start > 0) {
+			if (ratings[start - 1] > ratings[start] && plan[start - 1] <= plan[start]) {
+				plan[start - 1] = plan[start] + 1;
+			} else if (ratings[start - 1] < ratings[start] && plan[start - 1] >= plan[start]) {
+				plan[start] = plan[start - 1] + 1;
+			} else {
+				return;
+			}
+			start--;
+		}
+	}
+}

Copy List with Random Pointer.java

@@ -0,0 +1,43 @@
+A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.
+
+Return a deep copy of the list.
+
+/**
+ * Definition for singly-linked list with a random pointer.
+ * class RandomListNode {
+ *     int label;
+ *     RandomListNode next, random;
+ *     RandomListNode(int x) { this.label = x; }
+ * };
+ */
+public class Solution {
+    public RandomListNode copyRandomList(RandomListNode head) {
+    	if (head == null) return head;
+    	RandomListNode cur = head;
+    	while (cur != null) {
+    		RandomListNode newNode = new RandomListNode(cur.label);
+    		newNode.next = cur.next;
+    		cur.next = newNode;
+    		cur = newNode.next;
+    	}
+    	cur = head;
+    	while (cur != null) {
+    		if (cur.random != null) {
+    			cur.next.random = cur.random.next;
+    		}
+    		cur = cur.next.next;
+    	}
+    	cur = head.next;
+    	RandomListNode newHead = cur;
+    	RandomListNode old = head;
+    	while (old != null) {
+    		old.next = old.next.next;
+    		if (old.next != null) {
+    			cur.next = old.next.next;
+    		}
+    		cur = cur.next;
+    		old = old.next;
+    	}
+    	return newHead;
+    }
+}

Single Number.java

@@ -0,0 +1,14 @@
+Given an array of integers, every element appears twice except for one. Find that single one.
+
+Note:
+Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?
+
+public class Solution {
+	public int singleNumber(int[] A) {
+        int ret = A[0];
+        for (int i = 1; i < A.length; i++) {
+        	ret ^= A[i];
+        }
+        return ret;
+    }
+}