FEAT: add simple ac_automata of JS version

javascript/36_ac_automata/ac_automata.js

@@ -0,0 +1,103 @@
+
+MAX_LEN = 128;
+
+class ACNode {
+    constructor(data){
+        this.data = data;
+        this.children = new Array(MAX_LEN);
+        this.isEndingChar = false;
+        this.length = 0;
+        this.fail = null;
+    }
+}
+
+class ACTree {
+
+    constructor(data){
+        this.root = new ACNode('/')
+    }
+
+    insert (text) {
+        let node = this.root;
+        for (let char of text) {
+            let index = char.charCodeAt() + 1;
+            if(!node.children[index]) {
+                node.children[index] = new ACNode(char);
+            }
+            node = node.children[index];
+        }
+
+        node.isEndingChar = true;
+        node.length = text.length;
+    }
+
+    buildFailurePointer() {
+        let root = this.root;
+        let queue = [];
+        queue.push(root);
+
+        while (queue.length > 0) {
+            let p = queue.shift();
+
+            for (let i = 0; i < MAX_LEN; i++) {
+                let pc = p.children[i];
+                if (!pc) {
+                    continue;
+                } 
+
+                if(p == root) {
+                    pc.fail = root;
+                } else {
+                    let q = p.fail;
+                    while (q) {
+                        let qc = q.children[pc.data.charCodeAt() + 1];
+                        if(qc) {
+                            pc.fail = qc;
+                            break;
+                        }
+                        q = q.fail;
+                    }
+                    if(!q) {
+                        pc.fail = root;
+                    }
+                }
+                queue.push(pc);
+            }
+        }
+    }
+
+    match (text) {
+        let root = this.root;
+        let n = text.length;
+        let p = root;
+
+        for(let i = 0; i < n; i++) {
+            let idx = text[i].charCodeAt() + 1;
+            while(!p.children[idx] && p != root){
+                p = p.fail;
+            }
+
+            p = p.children[idx];
+            if(!p) {
+                p = root;
+            }
+
+            let tmp = p;
+            while ( tmp != root) {
+                if (tmp.isEndingChar == true) {
+                    console.log(`Start from ${i - p.length + 1}, length: ${p.length}`);
+                }
+                tmp = tmp.fail;
+            }
+        }
+    }
+}
+
+let automata = new ACTree();
+let patterns = ["at", "art", "oars", "soar"];
+for (let pattern of patterns) {
+    automata.insert(pattern);
+}
+
+automata.buildFailurePointer()
+automata.match("soarsoars");