Write a function to find the longest common prefix string amongst an array of strings. If there is no common prefix, return an empty string "".


Example 1:

Input: ["flower","flow","flight"]
Output: "fl"


Example 2:

Input: ["dog","racecar","car"]
Output: ""


Explanation: There is no common prefix among the input strings.
Note:

All given inputs are in lowercase letters a-z.

Solution 1 in C++

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        int arraySize = strs.size();
        if (arraySize<1) eturn "";
        
        int i;
        int s_len=strs[0].length();
        int prefixIndex=0;
        while(prefixIndex<s_len) {
            for(i=1;i<arraySize;i++) {
                if (strs[0][prefixIndex]!=strs[i][prefixIndex]) break;
            }
            if (i<arraySize) break;
            prefixIndex++;
        }
        if (prefixIndex) return strs[0].substr(0,prefixIndex);
        return "";        
    }
};

Solution 2 in Java - Complexity O(1), Time Complexity O(S)

public String longestCommonPrefix(String[] strs) {
    if (strs == null || strs.length == 0) return "";
    for (int i = 0; i < strs[0].length() ; i++){
        char c = strs[0].charAt(i);
        for (int j = 1; j < strs.length; j ++) {
            if (i == strs[j].length() || strs[j].charAt(i) != c)
                return strs[0].substring(0, i);             
        }
    }
    return strs[0];
}
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