package com.leetcode.leetcode.licm;

/**
 * @description: 劍指 Offer 05. 替換空格
 * 請實現一個函式，把字串 s 中的每個空格替換成"%20"。
 * <p>
 * <p>
 * <p>
 * 示例 1：
 * <p>
 * 輸入：s = "We are happy."
 * 輸出："We%20are%20happy."
 * <p>
 * <p>
 * 限制：
 * <p>
 * 0 <= s 的長度 <= 10000
 * @author: licm
 * @create: 2021-07-12 10:47
 **/
public class Lc_劍指Offer05替換空格 {
    /**
     * * 第一步 檢索當前字串有多少個空格,然後進行擴容
     * <p>
     * 第二部 將空格從後向前替換，利用雙指標
     *
     * @param s
     * @return
     */
    public static String replaceSpace(String s) {
        int count = 0;
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) == ' ') {
                count++;
            }
        }

        char[] charS = s.toCharArray();
        char[] newCharS = new char[charS.length + count * 2];
        for (int i = charS.length - 1; i >= 0; i--) {
            newCharS[i] = charS[i];
        }

        int left = charS.length - 1;
        int right = newCharS.length - 1;
       while(left<right) {
            if (newCharS[left] == ' ') {
                newCharS[right] = '0';
                newCharS[right - 1] = '2';
                newCharS[right - 2] = '%';
                right -= 2;

            } else {
                newCharS[right] = newCharS[left];
            }
            left--;
            right--;
        }
        String newStr = new String(newCharS, 0, newCharS.length);
        return newStr;
    }

    public static void main(String[] args) {
        String s = "We are happy.";
        System.out.println(replaceSpace(s));
    }
}