Analysis of JavaScript implementation method based on KMP algorithm_Basic knowledge

The core of the algorithm is the partial matching table and the fallback algorithm. The implementation of the partial matching table is as follows:

Copy code The code is as follows :

function kmpGetStrPartMatchValue(str) {
var prefix = [];
var suffix = [];
var partMatch = [];
for(var i =0,j=str.length;i var newStr = str.substring(0,i 1);
if(newStr.length == 1){
partMatch[ i] = 0;
} else {
[k] = newStr.slice(-k-1);
if(prefix[k] == suffix[k]){
partMatch[i] = prefix[k].length;
}
}
if(!partMatch[i]){
partMatch[i] = 0;
}
}
}
prefix.length = 0;
suffix.length = 0;
return partMatch;
}

//demovar t="ABCDABD";

console.log(kmpGetStrPartMatchValue(t));
//output:[0,0,0,0,1,2,0 ]


The fallback algorithm is implemented as follows:

Copy code The code is as follows:

function KMP(sourceStr,targetStr){

var partMatchValue = kmpGetStrPartMatchValue(targetStr);
var result = false;
for(var i=0,j=sourceStr.length;i for(var m=0,n=targetStr.length;m if(str.charAt(m) == sourceStr.charAt(i)){
if(m == targetStr.length-1){
result = true;
break;
} else {
                                                                               ; 🎜>} if (result) {
Break;
}
}
Return result;
}
var s = "bbc abcdabcdabcdabde"; t = "ABCDABD";
console.log(KMP(s,t));
//output: true