absolute-permutation

Author: prabaprakash

absolute-permutation.js

@@ -0,0 +1,99 @@
+
+// let permutation = [];
+// const permutate = (arr) => {
+//     for (let i = 0; i < arr.length - 1; i++) {
+//         let current = arr[i];
+
+//         let next = arr[i + 1]
+//         arr[i] = next;
+//         arr[i + 1] = current;
+//         permutation.push(arr.map(x=>x));
+//         arr[i + 1] = next;
+//         arr[i] = current;
+
+//     }
+// }
+
+// let arr = [1, 2, 3]
+// permutate(arr)
+// console.log(permutation);
+
+
+let permArr = [],
+    usedChars = [];
+function permute(input, diff) {
+    var i, ch;
+    for (i = 0; i < input.length; i++) {
+        // fixed 1, then process [2,3]
+        ch = input.splice(i, 1)[0];
+        // usedchars [1]
+        usedChars.push(ch);
+        if (input.length == 0) {
+            let bool = true;
+            for (let k = 0; k < usedChars.length; k++) {
+                if (Math.abs((usedChars[k] - (k + 1))) !== diff) {
+                    bool = false;
+                    break;
+                }
+            }
+            // console.log(usedChars);
+            if (bool) {
+                return usedChars;
+            }
+        }
+        // processing [2,3]
+        let res = permute(input, diff)
+        if (res.length > 0) {
+            return res;
+        }
+
+        input.splice(i, 0, ch);
+        usedChars.pop();
+    }
+    return [];
+};
+
+function validate(arr, diff) {
+    for (let k = 0; k < arr.length; k++) {
+        let index = k + 1;
+        let ithElement = arr[k];
+        if (Math.abs(index - ithElement) !== diff) {
+            return [];
+        }
+    }
+    return arr;
+}
+
+function permute2(permutation, diff) {
+    let length = permutation.length,
+        c = new Array(length).fill(0),
+        i = 1, k, p;
+    let arr = permutation.slice();
+    if (validate(arr, diff).length > 0)
+        return arr;
+
+    while (i < length) {
+        if (c[i] < i) {
+            k = i % 2 && c[i];
+            p = permutation[i];
+            permutation[i] = permutation[k];
+            permutation[k] = p;
+            ++c[i];
+            i = 1;
+            arr = permutation.slice();
+            if (validate(arr, diff).length > 0)
+                return arr;
+
+        } else {
+            c[i] = 0;
+            ++i;
+        }
+    }
+    return [];
+}
+n = 10;
+k = 5;
+
+let numbers = Array.from(Array(n), (_, i) => i + 1);
+
+console.log((permute2(numbers, k)));