替换字符串中所有子串问题描述输入三个字符串将主串s1中所有与字符串s2相同的子串替换成字符串s3.输入形式第一行输入主串s1第二行输入待替换的子串s2第三行输入替换字串s3.输出形式输出替换字串后的主创.样例输入A beautiful sunrise started the day with black clouds slowly lit by the bright yellow sun.sun moon样例输出A beautiful moonrise started the day with black clouds slowly lit by the bright yellow moon.评分标准填充各个函数利用已有函数完成子串替换.