剑指 Offer 05. 替换空格

/**
 * 剑指 Offer 05. 替换空格
 * @author wsq
 * @date 2020/09/08
 * 请实现一个函数，把字符串 s 中的每个空格替换成"%20"。
	示例 1：
	输入：s = "We are happy."
	输出："We%20are%20happy."
	
	限制：
	0 <= s 的长度 <= 10000
	
	链接：https://leetcode-cn.com/problems/ti-huan-kong-ge-lcof
 */
package notsubmit;

public class ReplaceSpace {
	/**
	 * java对于字符串的操作比较方便，没有用到对字符数组的倒序访问，减少重复移动元素的次数，提高效率
	 * @param s
	 * @return
	 */
    public String replaceSpace(String s) {
    	int numOfBlank = 0;
    	int originalLen = 0;
    	
    	for(char c: s.toCharArray()) {
    		++originalLen;
    		if(c == ' ') {
    			numOfBlank++;
    		}
    	}
    	int newLen = originalLen + 2 * numOfBlank;
    	StringBuilder sb = new StringBuilder(newLen);
    	for(char c: s.toCharArray()) {
    		if (c == ' ') {
				sb.append("%20");
			}else {
				sb.append(String.valueOf(c));
			}
    	}
    	return sb.toString();
    }
    
    public static void main(String[] args) {
		String s = "We are happy.";
		ReplaceSpace rs = new ReplaceSpace();
		String ans = rs.replaceSpace(s);
		System.out.println(ans);
	}
}