add kmp.js

kmp.js

@@ -0,0 +1,45 @@
+const genNext = (str) => {
+    const n = str.length
+    const next = new Array(n).fill(0)
+    next[0] = -1
+    next[1] = 0
+    for (let i = 2; i < n; i++) {
+        const Letter = str[i - 1] //now we want to find that something equal to Letter
+        let nextValue = i - 1
+        while (nextValue >= 0) {
+            if (Letter == str[next[nextValue]]) { //find
+                break
+            } else {
+                nextValue = next[nextValue]
+            }
+        }
+        if (nextValue == -1) {
+            next[i] = 0
+        } else {
+            next[i] = next[nextValue] + 1
+        }
+    }
+    return next
+}
+
+const kmp = (x, y) => {
+    const next = genNext(y)
+    console.log(next)
+    const n = x.length
+    const m = y.length
+    let i = 0, j = 0
+    while (i < n) {
+        while (j > -1 && x[i] != y[j]) {
+            j = next[j]
+        }
+        i++
+        j++
+        if (j == m) {
+            console.log(i - j)
+            j = 0 //when we have matched one, j should be zero
+        }
+
+    }
+}
+
+kmp("coniyconix", "conix")