kmp algorithm

String Matching/kmp.h

@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <string.h>
+#include <algorithm>
+using namespace std;
+#define maxn 100024
+
+struct KMP{
+    int next[maxn];
+    /*
+    next[j] represent the longest prefix-suffix of string
+    which length was k, namely p[0...j-1]. Because it means length,
+    just jump next[j] when t[i] not equal p[j].
+    */
+    void getnext(char *str){
+        int len = strlen(str);
+        int i, j;
+        for(i=2,j=next[1]=0; i<=len; i++){
+            while(j && str[j]!=str[i-1])
+                j = next[j];
+            if(str[j] == str[i-1])
+                j++;
+            next[i] = j;
+        }
+    }
+    void find(char *t, char *p){
+        getnext(p);
+        int i, j;
+        for(i=0,j=0; i<strlen(t); i++){
+            while(j && t[i]!=p[j])
+                j = next[j];
+            if(t[i] == p[j])
+                j++;
+        }
+        printf("%s%s\n",t,p+j);
+    }
+    /*
+    next[j] represent the end index of longest prefix-suffix,
+    namely p[0...j]. Because it means index, jump next[j]
+    when t[i] not equal p[j+1].
+    */
+    void get_next(char *str){
+        int len = strlen(str);
+        int i, j;
+        for(i=1; j=next[0]=-1; i<len; i++){
+            while(j>=0 && str[j+1]!=str[i])
+                j = next[j];
+            if(str[j+1] == str[i])
+                j++;
+            next[i] = j;
+        }
+    }
+    void solve(char *t, char *p){
+        int i, j;
+        for(i=0,j=-1; i<strlen(t); i++){
+            while(j>=0 && p[j+1]!=t[i])
+                j = next[j];
+            if(p[j+1] == t[i])
+                j++;
+        }
+    }
+};
+char str[maxn], p[maxn];
+KMP kmp;
+
+int main(){
+    while(scanf("%s",str) != EOF){
+        strcpy(p,str);
+        reverse(p,p+strlen(p));
+        kmp.find(str,p);
+    }
+    return 0;
+}