replace_0_with_1_to_get_lonegest_seq_of_1s.java

/**
     * 1) Window can have only one zero.
     *
     * 2) Window's right border is expanded to the right on each step.
     *
     * 3) When a new zero is detected the left border
     * is set to prevZeroIndex+1 to exclude the old zero.
     *
     * 3) On every step we check if current window is the largest known window.
     */
    private static int slidingWindow(int[] a) {
        int wStart = 0;
        int wEnd = 0;

        int globalZeroIndex = 0;
        int globalLength = 0;

        int currentZeroIndex = 0;
        int currentLength = 0;

        for (int i = 0; i < a.length; i++) {
            wEnd = i;
            if (a[i] == 1) {
                currentLength++;
            } else {
                wStart = currentZeroIndex + 1;
                currentLength = wEnd - wStart + 1;
                currentZeroIndex = wEnd;
            }

            if (currentLength > globalLength) {
                globalZeroIndex = currentZeroIndex;
                globalLength = currentLength;
            }
        }

        return globalZeroIndex;
    }