443. String Compression

Easy

Given an array of characters, compress it in-place.

The length after compression must always be smaller than or equal to the original array.

Every element of the array should be a character (not int) of length 1.

After you are done modifying the input array in-place, return the new length of the array.

 

Follow up:
Could you solve it using only O(1) extra space?

 

Example 1:

Input:
["a","a","b","b","c","c","c"]

Output:
Return 6, and the first 6 characters of the input array should be: ["a","2","b","2","c","3"]

Explanation:
"aa" is replaced by "a2". "bb" is replaced by "b2". "ccc" is replaced by "c3".

 

Example 2:

Input:
["a"]

Output:
Return 1, and the first 1 characters of the input array should be: ["a"]

Explanation:
Nothing is replaced.

 

Example 3:

Input:
["a","b","b","b","b","b","b","b","b","b","b","b","b"]

Output:
Return 4, and the first 4 characters of the input array should be: ["a","b","1","2"].

Explanation:
Since the character "a" does not repeat, it is not compressed. "bbbbbbbbbbbb" is replaced by "b12".
Notice each digit has it's own entry in the array.

 

Note:

1. All characters have an ASCII value in [35, 126].
2. 1 <= len(chars) <= 1000.

 

package leetcode.easy;

public class StringCompression {
	public int compress(char[] chars) {
		int indexAns = 0, index = 0;
		while (index < chars.length) {
			char currentChar = chars[index];
			int count = 0;
			while (index < chars.length && chars[index] == currentChar) {
				index++;
				count++;
			}
			chars[indexAns] = currentChar;
			indexAns++;
			if (count != 1) {
				for (char c : String.valueOf(count).toCharArray()) {
					chars[indexAns] = c;
					indexAns++;
				}
			}
		}
		return indexAns;
	}

	@org.junit.Test
	public void test() {
		char[] chars1 = { 'a', 'a', 'b', 'b', 'c', 'c', 'c' };
		char[] chars2 = { 'a' };
		char[] chars3 = { 'a', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b', 'b' };
		System.out.println(compress(chars1));
		System.out.println(compress(chars2));
		System.out.println(compress(chars3));
	}
}