## Goldman Sachs Interview Question for Backend Developers

Country: United States
Interview Type: In-Person

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Is the order fixed in which you have to visit the channels or can you pick the order?
what is the starting start and end channel used for? Does it mean if you start the channel "start" was running and channel "end" should be set after visiting all channels in that array?

I assume the order is fixed and we can create an array C [start, A[0], A[1], ... ,A[n-1], end] that is the sequence I have to tune channels in.

I need seiling(log10(C[i]+1)) key hits to enter the number C[i]
I need ABS(C[i-1] - C[i]) key hits to tune in using + or -
I need ABS(C[i-2] - C[i]) + 1 key hits to tune in using back and + or -
I will have to use the sum of above min for each C[i] 0 < i < n key hits to tune in all assuming C[0] = start was tuned in when I started.

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``````public static void main(String[] args) {
String[] cnos = { "2", "4", "600", "60", "100", "10", "50", "5", "77" };
String start = "60";
String end = "50";
int stInd = -1;
int eInd = -1;
sort(cnos, 0, cnos.length, new HashMap<String, Double>());

for (int i = 0; i < cnos.length; i++) {
if (cnos[i].equals(start)) {
stInd = i;
}
}
rotate(cnos, stInd);
for (int i = 0; i < cnos.length; i++) {
if (cnos[i].equals(end)) {
eInd = i;
}
}
swap(cnos, eInd, cnos.length-1);
int[] minclicks = new int[1];
minclicks[0] = Integer.MAX_VALUE;
countclicks(start, end, cnos, "", cnos.length, 0, minclicks, 0, cnos.length - 1);
System.out.println(minclicks[0]);
}

public static int countclicks(String start, String end, String[] cnos, String ch, int n, int clicks,
int[] minclicks, int stInd, int len) {

if(n < 0)
return clicks;

if (ch.equals(end) && n == 0) {
minclicks[0] = Math.min(clicks, minclicks[0]);
return clicks;
}

String last = start;
for (int i = stInd; i <= len; i++) {
clicks = countclicks(start, end, cnos, cnos[i], n-1, clicks+clicks(last, cnos[i]), minclicks, i + 1, len);
last = cnos[i];
}
return clicks;
}

public static void rotate(String[] arr, int p){
int n = p;
int m = arr.length;
while(n > 0){
int i = p;
String t = arr[i];
int x = m;
while(i >= 0 && x > 0){
if(i == 0)
i = arr.length;
String te = arr[i-1];
arr[i-1] = t;
t = te;
i--;
x--;
}
n--;
p--;
}
}

public static int clicks(String lastChannel, String nextChannel) {

int lch = Integer.parseInt(lastChannel);
int nch = Integer.parseInt(nextChannel);
if (lch - nch == 1 || lch - nch == -1)
return 1;

int index = -1;
if (lastChannel.length() <= nextChannel.length()) {
index = nextChannel.indexOf(lastChannel);
if (index == 0)
return nextChannel.length() - lastChannel.length();
} else {
index = lastChannel.indexOf(nextChannel);
if (index == 0)
return lastChannel.length() - nextChannel.length();
}

return nextChannel.length();

}

public static void sort(String[] arr, int l, int h, Map<String, Double> hMap) {
if(l >= h)
return;
int n = arr.length;
String mid = arr[(h - l) / 2 + l];
int i = 0;
int j = n - 1;

if (hMap.get(mid) == null)
hMap.put(mid, hash(mid));
double midhash = hMap.get(mid);

while (i < j) {
if (hMap.get(arr[i]) == null)
hMap.put(arr[i], hash(arr[i]));
if (hMap.get(arr[j]) == null)
hMap.put(arr[j], hash(arr[j]));

double iVal = hMap.get(arr[i]);
double jVal = hMap.get(arr[j]);

while (iVal < midhash) {
i++;
if (hMap.get(arr[i]) == null)
hMap.put(arr[i], hash(arr[i]));
iVal = hMap.get(arr[i]);
}
while (jVal > midhash) {
j--;
if (hMap.get(arr[j]) == null)
hMap.put(arr[j], hash(arr[j]));
jVal = hMap.get(arr[j]);
}
if (i <= j) {
swap(arr, i, j);
i++;
j--;
}
}
if (i < h)
sort(arr, i, h, hMap);
if (j > l)
sort(arr, l, j, hMap);
}

public static double hash(String str) {
char[] carr = str.toCharArray();
int i = 0;

double hash = 0;
while (i <= carr.length - 1) {
hash += Integer.parseInt(String.valueOf(carr[i]))+0.1;
i++;
}
return hash;
}

public static void swap(String[] arr, int i, int j) {
String t = arr[i];
arr[i] = arr[j];
arr[j] = t;
}``````

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