leetcode (14) - Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

char* longestCommonPrefix(char** strs, int strsSize) {
    int min_length = 0, min_index=0, i, j,tmp ;
    int  flag=1;
    if (strsSize == 0) return "";
    if (strsSize == 1) return strs[0];
    
    if ((strlen(strs[0])) > 0) 
        min_length = strlen(strs[0]);
        

    for (i = 0; i < strsSize; i++) {      // 首先找出最短的長度，因爲最長前綴是拿着最短的字符串去比較
        tmp=strlen(strs[i]);
        if (tmp < min_length) {
            min_length = tmp;
            min_index = i;

        }

    }

    if (min_length == 0) return "";
       
    char* ret = malloc((min_length)*sizeof(char));
    *ret="";
    for (j = 0; j < min_length; j++) {    //遍歷最短字符串的每個字符

        for (i = 0; i < strsSize; i++) {    //遍歷字符串數組，和最短字符串的每個字符作比較，如果發現有不相等的，就跳出兩層for循環
            if (strs[min_index][j] != strs[i][j]) {
                flag = 0;
                printf("%d", flag);
                break;
            }
        }    
        if (flag==1) {
            ret[j]=strs[min_index][j];

        } else {
            ret[j]='\0';
            return ret;
        }
    }
    ret[j]='\0';
    return ret;
}

Note:  其實不用找出最短的字符串，任意取字符串作比較即可。