Leetcode443 压缩字符串 双指针原地压缩算法

　　提前验证抽象的正确性，尤其是边界问题在抽象中是否可以被很好的解决。然后以抽象的角度去考虑问题，简化问题。

　　比如双指针，提前验证可以使用双指针方法后，只需要考虑区间何时退出以及退出时的逻辑即可。

　　双指针原地压缩算法 JAVA：

    public final int compress(char[] chars) {
        int write = 0, left = 0, right = 0, len = chars.length;
        while (left < len) {
            while (right < len && chars[left] == chars[right]) right++;
            int currLen = right - left;
            if (currLen <= 1) {
                chars[write++] = chars[left++];
                continue;
            }
            chars[write++] = chars[left];
            char[] numChars = ("" + currLen).toCharArray();
            for (char c : numChars) chars[write++] = c;
            left = right;
        }
        return write;
    }

　　JS：

/**
 * @param {character[]} chars
 * @return {number}
 */
var compress = function (chars) {
    let write = 0, right = left = 0, len = chars.length;
    while (left < len) {
        while (right < len && chars[left] == chars[right]) right++;
        let currLen = right - left;
        if (currLen <= 1) chars[write++] = chars[left++];
        else {
            chars[write++] = chars[left];
            let currLenStr = currLen + '';
            for (let i = 0; i < currLenStr.length; i++) chars[write++] = currLenStr.charAt(i);
            left = right;
        }
    }
    return write;
};