2016 Update

Task/Equilibrium-index/JavaScript/equilibrium-index.js

@@ -1,21 +1,19 @@
-function equilibrium (array) {
-  var equilibriums = [];
-
-  array.forEach(function(_, idx, arr) {
-    var left = 0, right = 0;
-
-    for (var i = 0; i < arr.length; i++) {
-      if (i < idx) {
-        left += array[i];
-      } else if (i > idx) {
-        right += array[i];
-      }
-    }
-
-    if (left === right) equilibriums.push(idx);
-  });
-
-  return equilibriums;
+function equilibrium(a) {
+  var N = a.length, i, l = [], r = [], e = []
+  for (l[0] = a[0], r[N - 1] = a[N - 1], i = 1; i<N; i++)
+    l[i] = l[i - 1] + a[i], r[N - i - 1] = r[N - i] + a[N - i - 1]
+  for (i = 0; i < N; i++)
+    if (l[i] === r[i]) e.push(i)
+  return e
 }
 
-console.log(equilibrium([-7,1,5,2,-4,3,0]));
+// test & output
+[ [-7, 1, 5, 2, -4, 3, 0], // 3, 6
+  [2, 4, 6], // empty
+  [2, 9, 2], // 1
+  [1, -1, 1, -1, 1, -1, 1], // 0,1,2,3,4,5,6
+  [1], // 0
+  [] // empty
+].forEach(function(x) {
+  console.log(equilibrium(x))
+});