View Compilation Error

0_0_27579508_4014.cpp: In function 'int KmpIndex()':
0_0_27579508_4014.cpp:20:22: error: 's' was not declared in this scope
         while(j!=-1&&s[i]!=t[j])///当前字符匹配失败或j!=-1,令j=next[j],重新遍历
                      ^
0_0_27579508_4014.cpp:20:28: error: 't' was not declared in this scope
         while(j!=-1&&s[i]!=t[j])///当前字符匹配失败或j!=-1,令j=next[j],重新遍历
                            ^