suffix array added

Author: Nadim-Mahmud

Source/String/Suffix Array.cpp

@@ -0,0 +1,56 @@
+/**
+    Description : it gives all suffixes in sorted form on an array
+    the array contains starting position of suffixes in sorted order
+    Longest common prefix array contains long match with the previous suffix in sorted form
+    Complexity : O(n^2Logn)
+    Ex :
+
+    0 banana                          5 a
+    1 anana     Sort the Suffixes     3 ana
+    2 nana      ---------------->     1 anana
+    3 ana        alphabetically       0 banana
+    4 na                              4 na
+    5 a                               2 nana
+    So the suffix array for "banana" is {5, 3, 1, 0, 4, 2}
+*/
+
+#define MX 10005
+
+int sfa[10009],pos[10009],tmp[10009],lcp[10009],gap=1,ln;
+char ss[10009];
+bool scmp(int a,int b)
+{
+    if(pos[a]!=pos[b])return pos[a]<pos[b];
+    a+=gap;
+    b+=gap;
+    return (a<ln&&b<ln)?pos[a]<pos[b]:a>b;
+
+}
+void buildsa()
+{
+    int i,j;
+    ln=strlen(ss);
+    for(i=0;i<=ln;i++){
+        sfa[i]=i;
+        pos[i]=ss[i];
+    }
+    for(gap=1;;gap*=2){
+        sort(sfa,sfa+ln,scmp);
+        for(i=0;i<ln;i++){
+            tmp[i+1]=tmp[i]+scmp(sfa[i],sfa[i+1]);
+        }
+        for(i=0;i<ln;i++)pos[sfa[i]]=tmp[i];
+        if(tmp[i]==ln-1)break;
+    }
+}
+void buildlcp()
+{
+    int i,j,k;
+    for(i=0,k=0;i<ln;i++){
+        if(pos[i]==ln-1)continue;
+        for(j=sfa[pos[i]+1];ss[i+k]==ss[j+k];)k++;
+        lcp[pos[i]]=k;
+        if(k)k--;
+    }
+    lcp[ln-1] = 0;
+}