题目及测试
package sword004;
/** 题目描述： 请实现一个函数，将字符串的每个空格替换为"%20"。* 例如输入"We are happy",则输出"We%20are%20happy."。*/public class main {public static void main(String[] args) {String [] testTable = {"hello","A man, a plan, a canal: Panama","av12,./34\\45"};for (String ito : testTable) {test(ito);}}private static void test(String ito) {Solution solution = new Solution();String rtn;long begin = System.currentTimeMillis();System.out.print(ito); System.out.println();//开始时打印数组rtn= solution.replace(ito);//执行程序long end = System.currentTimeMillis(); System.out.println("rtn=" );System.out.print(rtn);System.out.println();System.out.println("耗时：" + (end - begin) + "ms");System.out.println("-------------------");}}
解法1（成功）
先计算input中空格的数目count，然后建立大小为length+2*count的新char数组，然后双指针遍历新旧数组，给新数组赋值，遇到旧数组的空格，就新数组设置3个值。
package sword004;import java.util.Arrays;public class Solution {public String replace(String input) {if(input == null) {return input;}int length = input.length();if(length ==0) {return input;}int count =0;for(int i=0;i<length;i++) {if(input.charAt(i) == ' ') {count++;}}if(count == 0) {return input;}int totalLength = length +2 * count;char[] array = new char[totalLength];int j = 0;for(int i=0;i<length;i++) {if(input.charAt(i) == ' ') {array[j++] = '%';array[j++] = '2';array[j++] = '0';}else {array[j++] = input.charAt(i);}} return new String(array);}}