diff --git a/Misc/KMP.java b/Misc/KMP.java new file mode 100644 index 000000000000..c97c248b480a --- /dev/null +++ b/Misc/KMP.java @@ -0,0 +1,55 @@ + +/* +Implementation of Knuth–Morris–Pratt algorithm +Usage: +final String T = "AAAAABAAABA"; +final String P = "AAAA"; +KMPmatcher(T, P); +*/ +public class KMP { + + // find the starting index in string T[] that matches the search word P[] + public void KMPmatcher(final String T, final String P) { + final int m = T.length(); + final int n = P.length(); + final int[] pi = computePrefixFunction(P); + int q = 0; + for (int i = 0; i < m; i++) { + while (q > 0 && T.charAt(i) != P.charAt(q)) { + q = pi[q - 1]; + } + + if (T.charAt(i) == P.charAt(q)) { + q++; + } + + if (q == n) { + System.out.println("Pattern starts: " + (i + 1 - n)); + q = pi[q - 1]; + } + } + + } + + // return the prefix function + private int[] computePrefixFunction(final String P) { + final int n = P.length(); + final int[] pi = new int[n]; + pi[0] = 0; + int q = 0; + for (int i = 1; i < n; i++) { + while (q > 0 && P.charAt(q) != P.charAt(i)) { + q = pi[q - 1]; + } + + if (P.charAt(q) == P.charAt(i)) { + q++; + } + + pi[i] = q; + + } + + return pi; + } +} diff --git a/Searches/BinarySearch.java b/Searches/BinarySearch.java index 3949f6a86f02..535442c87409 100644 --- a/Searches/BinarySearch.java +++ b/Searches/BinarySearch.java @@ -23,7 +23,7 @@ public static > int BS(T array[], T key, int lb, int ub) if ( lb > ub) return -1; - int mid = (ub+lb)/2; + int mid = (ub+lb) >>> 1; int comp = key.compareTo(array[mid]); if (comp < 0)