Formatted question description: https://leetcode.ca/all/443.html

# 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.

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.

Companies:
Microsoft, Goldman Sachs, Bloomberg

Related Topics:
String

Similar Questions:

## Solution 1.

// OJ: https://leetcode.com/problems/string-compression/

// Time: O(N)
// Space: O(1)
class Solution {
public:
int compress(vector<char>& chars) {
int i = 0, N = chars.size(), j = 0, r = 0;
while (i < N) {
j = i + 1;
while (j < N && chars[j] == chars[i]) ++j;
chars[r++] = chars[i];
if (j - i > 1) {
int cnt = j - i, pow = 1;
while (cnt / (pow * 10)) pow *= 10;
while (pow) {
chars[r++] = '0' + cnt / pow;
cnt %= pow;
pow /= 10;
}
}
i = j;
}
return r;
}
};


Java

class Solution {
public int compress(char[] chars) {
if (chars == null)
return 0;
int length = chars.length;
if (length <= 1)
return length;
int index = 0;
char prevChar = chars;
int count = 1;
for (int i = 1; i < length; i++) {
char c = chars[i];
if (c == prevChar)
count++;
else {
chars[index] = prevChar;
index++;
if (count > 1) {
String countStr = String.valueOf(count);
int countLength = countStr.length();
for (int j = 0; j < countLength; j++) {
chars[index] = countStr.charAt(j);
index++;
}
count = 1;
}
prevChar = c;
}
}
if (count > 0) {
chars[index] = prevChar;
index++;
if (count > 1) {
String countStr = String.valueOf(count);
int countLength = countStr.length();
for (int j = 0; j < countLength; j++) {
chars[index] = countStr.charAt(j);
index++;
}
}
}
return index;
}
}