Remove Duplicates from Sorted Array II

Author: mengli

RemoveDuplicatesFromSortedArrayII.java

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+/**
+ * Follow up for "Remove Duplicates": What if duplicates are allowed at most twice?
+ * 
+ * For example,
+ * 
+ * Given sorted array A = [1,1,1,2,2,3],
+ * 
+ * Your function should return length = 5, and A is now [1,1,2,2,3].
+ *
+ */
+public class RemoveDuplicatesFromSortedArrayII {
+	public int removeDuplicates(int[] A) {
+		int length = A.length;
+		if (length < 3)
+			return length;
+		int slow = 0, fast = 1, idx = 0;
+		while (fast < length) {
+			while (fast < length && A[fast] == A[slow]) {
+				fast++;
+			}
+			if (fast - slow <= 2) {
+				while (slow < fast) {
+					A[idx++] = A[slow++];
+				}
+			} else {
+				A[idx++] = A[slow++];
+				A[idx++] = A[slow++];
+				slow = fast;
+			}
+			fast++;
+		}
+		while (slow < length) {
+			A[idx++] = A[slow++];
+		}
+		return idx;
+	}
+}