solves 5.3 with help and hints

Author: amejiarosario

src/05-bits/03-flip-bit-to-win.js

@@ -0,0 +1,61 @@
+/**
+ * 5.3 Flip Bit to Win: You have an integer and you can flip exactly one bit from a 0 to a 1. Write code to find the length of the longest sequence of 1syou could create.
+
+ EXAMPLE
+
+ Input: 1775 (or: 11011101111)
+ Output: 8
+
+ * @param number
+ */
+function flipBitToWin(number) {
+  // keep two counters for previous and current ones
+  let previous = 0;
+  let current = 0;
+  let max = 0;
+
+  while(number > 0) {
+    if(number & 1) {
+      current++;
+    } else {
+      if(previous > 0) {
+        max = Math.max(current + previous + 1, max);
+      }
+
+      previous = current;
+      current = 0;
+    }
+
+    number >>= 1;
+  }
+
+  if(previous > 0) {
+    max = Math.max(current + previous + 1, max);
+  } else {
+    max = Math.max(current, max);
+  }
+
+  return max;
+}
+
+module.exports = flipBitToWin;
+
+/*
+
+Brute force
+  1. number to binary string
+  2. iterate to find 0's
+  3. change the 0 to 1 and count contiguous 1's
+  4. flip back to zero and repeat until last bit
+  5. print max contiguous 1's
+
+O (x^2), where x is the number of bits
+
+Hints: #159, #226, #314, #352
+
+  # Start with a brute force solution. Can you try all possibilities?
+  # Flipping a 0 to a 1 can merge two sequences of 1s-but only if the two sequences are separated by only one O.
+  # Each sequence can be lengthened by merging it with an adjacent sequence (if any) or just flipping the immediate neighboring zero.You just need to find the best choice.
+  # Try to do it in linear time, a single pass, and 0 (1) space.
+
+ */

src/05-bits/03-flip-bit-to-win.spec.js

@@ -0,0 +1,20 @@
+const expect = require('chai').expect;
+const flipBitToWin = require('./03-flip-bit-to-win');
+
+describe('Bit Manipulation: flipBitToWin', function() {
+  it('all ones', function() {
+    expect(flipBitToWin(0b11111111)).to.equal(8);
+  });
+
+  it('all ones but one', function() {
+    expect(flipBitToWin(0b11111101)).to.equal(8);
+  });
+
+  it('two zeros at the beginning', function() {
+    expect(flipBitToWin(0b11110101)).to.equal(6);
+  });
+
+  it('two zeros at the end', function() {
+    expect(flipBitToWin(0b10101111)).to.equal(6);
+  });
+});