leetcode 最长回文字符串，我的dp算法一直在本地测试通过，在leetcode上结果错误

以下是我的源代码：
`int dp1000 = {0};
char longestPalindrome(char s) {

int length = strlen(s);
int i = 0, j = 0;
char lstr[1000] = "";
int left = 0, maxLen = 1; 

if (!length) return "";
if (length == 1)  return s;

for (j = 0; j < length; j++) dp[j][j] = 1;

for (j = 0; j < length - 1; j++) {
    if (s[j] == s[j+1]) {
       dp[j][j+1] = 1;
       left = j;
       maxLen = 2;
    }
}
        
for (int len = 3; len <= length; len++) {  
    for (int i = 0; i < length - len + 1; i++) {  
      int j = i + len - 1;  
      if (s[i] == s[j] && dp[i+1][j-1]) {  
        dp[i][j] = 1;  
        left = i;  
        maxLen = len;  
      }  
    }  
 }  
 
 for ( i = left, j = 0; i < left + maxLen; i++,j++) {
     lstr[j] = s[i];
 }
//strncpy(lstr, s + left, maxLen);

return lstr;

}`

输入为"aaabaaaa" leetcode输出为"aaabaaaa"应该输出为"aaabaaa",在本地输出是“aaabaaa