求一个字符串的有效长度。#include stdiohint countchar a int i=0; whileai!=0【1】; 【2】;main char a50; 【3】; getsa; t=【4】; printfdnt;

#include "stdio.h" int count(char a[]) { int i=0; while(a[i]!='\0') { i++; } return i; } main() { char a[50]; printf("请输入一个字符串："); gets(a); int t=count(a); printf("有效长度为：%d\n",t); }