Algorithms/ArrayUtils.java at master · iensen/Algorithms · GitHub

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packageiensen;

importjava.util.Random;

/**
 * Created with IntelliJ IDEA.
 * User: iensen
 * Date: 2/24/13
 * Time: 10:15 AM
 * To change this template use File | Settings | File Templates.
 */
publicclassArrayUtils
{
publicstaticvoidshuffle(Object[] a) {
intn = a.length;
Randomrandom = newRandom();

for (inti = 0; i < n; i++) {
intchange = i + random.nextInt(n - i);
swap(a, i, change);
 }
 }

privatestaticvoidswap(Object[] a, inti, intchangeIdx) {
Objecttemp = a[i];
a[i] = a[changeIdx];
a[changeIdx] = temp;
 }


publicstaticintlower_bound(Comparable[] arr, Comparablekey) {
intlen = arr.length;
intlo = 0;
inthi = len-1;
intmid = (lo + hi)/2;
while (true) {
intcmp = arr[mid].compareTo(key);
if (cmp == 0 || cmp > 0) {
hi = mid-1;
if (hi < lo)
returnmid;
 } else {
lo = mid+1;
if (hi < lo)
returnmid<len-1?mid+1:-1;
 }
mid = (lo + hi)/2;
 }
 }

publicstaticintupper_bound(Comparable[] arr, Comparablekey) {
intlen = arr.length;
intlo = 0;
inthi = len-1;
intmid = (lo + hi)/2;
while (true) {
intcmp = arr[mid].compareTo(key);
if (cmp == 0 || cmp < 0) {
lo = mid+1;
if (hi < lo)
returnmid<len-1?mid+1:-1;
 } else {
hi = mid-1;
if (hi < lo)
returnmid;
 }
mid = (lo + hi)/2;
 }
 }


publicstaticvoidreverse(int []a)
 {
for(inti = 0; i < a.length/2; i++)
 {
inttemp = a[i];
a[i] = a[a.length - i - 1];
a[a.length - i - 1] = temp;
 }
 }


booleannext_permutation(int[] p) {
for (inta = p.length - 2; a >= 0; --a)
if (p[a] < p[a + 1])
for (intb = p.length - 1;; --b)
if (p[b] > p[a]) {
intt = p[a];
p[a] = p[b];
p[b] = t;
for (++a, b = p.length - 1; a < b; ++a, --b) {
t = p[a];
p[a] = p[b];
p[b] = t;
 }
returntrue;
 }
returnfalse;
 }
}