/** Created by psingh on 5/12/16. Problem 5.12 from EPI */
public class UnifRandomNumberGenerator {
private static final int NUM_TESTS = (int) Math.pow(10, 6);
private static int zeroOneRandom() {
Random rgen = new Random();
return rgen.nextInt(2);
}
private static int UnifRandom(int lowerBound, int upperBound) {
final int numOutcomes = upperBound - lowerBound + 1;
int result;
do {
result = 0;
for (int i = 0; (1 << i) < numOutcomes; ++i) result = (result << 1) | zeroOneRandom();
} while (result >= numOutcomes);
return lowerBound + result;
}
public static void main(String[] args) throws Exception {
if (args.length == 2) {
int a, b;
a = Integer.parseInt(args[0]);
b = Integer.parseInt(args[1]);
int x = UnifRandom(a, b);
assert (a <= x && x <= b);
} else {
Supplier<CloneableInputsMap> formInputs =
() -> {
Random rgen = new Random();
int a = rgen.nextInt(100);
int b = rgen.nextInt(100) + a + 1;
CloneableInputsMap inputs = new CloneableInputsMap();
inputs.addInteger("a", a);
inputs.addInteger("b", b);
return inputs;
};
Function<CloneableInputsMap, Integer> runAlg =
(inputs) -> UnifRandom(inputs.getInteger("a"), inputs.getInteger("b"));
BiFunction<Integer, CloneableInputsMap, Boolean> checkResults =
(observed, extra) ->
extra.getInteger("a") <= observed && observed <= extra.getInteger("b");
AlgVerifierInterfaces<Integer, CloneableInputsMap> algVerifier =
new InputOutputVerifier<>(checkResults);
AlgorithmFactory algorithmFactory =
new AlgorithmRunnerAndVerifier<>(
"UnifRandomNumberGenerator", NUM_TESTS, formInputs, runAlg, algVerifier);
algorithmFactory.run();
}
}
}
/**
* Created by psingh on 5/28/16. Problem 7.2
*
* @summary Delete each "b" and replace each "a" with a "dd" in a given character array.
* <p><u><b>Strategy</b></u> 1) On the first pass, count the number of non-"b" characters and
* the number of "a", using the variables writeIdx and aCnt, respectively. For each non-"b"
* character, write it to writeIdx on the first pass.
* <p>The desired string will be writeIdx + aCnt characters long. Assume the character array is
* big enough.
* <p>2) Start writing final string backwards, from right to left, while iterating from writeIdx
* down to 0, taking care to write "a" as "dd".
*/
public class ReplaceAndRemove {
private static final int ARR_LEN = (int) Math.pow(10, 2);
private static final int NUM_TESTS = (int) Math.pow(10, 6);
/**
* @param s character array
* @return length of string in character array after algorithm.
*/
private static int replaceAndRemove(char[] s, int len) {
int writeIdx = 0, aCnt = 0;
// First pass: ignore "b"s, write everything else. Count the number of "a"s
for (int i = 0; i < len; ++i) {
if (s[i] != 'b') {
s[writeIdx++] = s[i];
}
if (s[i] == 'a') {
aCnt += 1;
}
}
// Second pass: iterate backwars (right to left), while replacing "a"s with "dd"s
int finalSize = writeIdx + aCnt;
int currIdx = writeIdx - 1; // iterate from right to left over the characters we just wrote
writeIdx = finalSize - 1; // start writing right to left from where final string will end
while (currIdx >= 0) {
if (s[currIdx] == 'a') {
s[writeIdx--] = 'd';
s[writeIdx--] = 'd';
} else {
s[writeIdx--] = s[currIdx];
}
currIdx -= 1;
}
return finalSize;
}
private static String knownOutput(char[] s, int len) {
String str = new String(s, 0, len);
str = str.replace("b", "");
str = str.replace("a", "dd");
return str;
}
public static void main(String[] args) throws Exception {
Supplier<CloneableInputsMap> formInputs =
() -> {
CloneableInputsMap inputs = new CloneableInputsMap();
Random rgen = new Random();
char[] s = new char[(ARR_LEN << 1) + 1];
MiscHelperMethods.randCharArray(() -> (char) ('a' + rgen.nextInt(26)), ARR_LEN, s);
inputs.addCharArray("s", s);
inputs.addInteger("len", ARR_LEN);
return inputs;
};
Function<CloneableInputsMap, Integer> runAlg =
(inputs) -> replaceAndRemove(inputs.getCharArray("s"), inputs.getInteger("len"));
Function<CloneableInputsMap, Integer> knownOutput =
(inputs) -> {
String expected = knownOutput(inputs.getCharArray("s"), inputs.getInteger("len"));
inputs.addCharArray("s", expected.toCharArray());
return expected.length();
};
Function<CloneableInputsMap, CloneableInputsMap> saveExtraResults =
(inputs) -> {
CloneableInputsMap extraResults = new CloneableInputsMap();
extraResults.addCharArray("s", inputs.getCharArray("s"));
return extraResults;
};
AlgVerifierInterfaces.QuadFunction<
Integer, Integer, CloneableInputsMap, CloneableInputsMap, Boolean>
checkAns =
(observed, expected, algExtraResults, expExtraResults) ->
observed.equals(expected)
&& algExtraResults.getCharArray("s").length >= observed
&& expExtraResults.getCharArray("s").length >= observed
&& String.valueOf(algExtraResults.getCharArray("s"))
.substring(0, observed)
.equals(
String.valueOf(expExtraResults.getCharArray("s"))
.substring(0, observed));
AlgVerifierInterfaces<Integer, CloneableInputsMap> algVerifier =
new OutputOutputExtraExtraVerifier<>(checkAns);
AlgorithmFactory algorithmFactory =
new AlgorithmRunnerAndVerifier<>(
"Replace and Remove",
NUM_TESTS,
formInputs,
runAlg,
knownOutput,
saveExtraResults,
algVerifier);
System.out.println(
String.format("Running algorithms on character arrays of length %d...", ARR_LEN));
// algorithmFactory.setSequential();
algorithmFactory.run();
}
}
