14. Longest Common Prefix

14. Longest Common Prefix

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

/**
 * @param {string[]} strs
 * @return {string}
 */
var longestCommonPrefix = function(strs) {
    
    //每次都拿一个最长公共前序列去比较得了  比如string[] = ["aa","ab","ap"]
    // aa 和 ab 比较是 a ,  然后 a 和 ap 去比较  还是 a
    
    function lcp(a,b){
         
        var min_len = Math.min(a.length,b.length);
        var count = 0;
        for(var i = 0; i< min_len;i++){
            if(a[i] == b[i]){
                count++;
            }else{
                break;
            }
        }
        
        return a.substr(0,count);       
    }
    
    var slen = strs.length;
    
    if(slen == 0){
        
        return "";
    }
    
    if(slen == 1){
        return strs[0];
    }
    
    var pattern = strs[0]
    
    for(var i = 1; i<slen;i++){
       pattern =  lcp(pattern,strs[i]);
    }
    
    return pattern;
};