adding C module for longuest common subsequence

rosalind/lcs.c

@@ -0,0 +1,46 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define MAX(A,B) (((A)>(B))? (A) : (B))
+
+char * lcs(const char *a,const char * b) {
+    int lena = strlen(a)+1;
+    int lenb = strlen(b)+1;
+
+    int bufrlen = 40;
+    char bufr[40], *result;
+
+    int i,j;
+    const char *x, *y;
+    int *la = calloc(lena*lenb, sizeof( int));
+    int  **lengths = malloc( lena*sizeof( int*));
+    for (i=0; i<lena; i++) lengths[i] = la + i*lenb;
+
+    for (i=0,x=a; *x; i++, x++) {
+        for (j=0,y=b; *y; j++,y++ ) {
+            if (*x == *y) {
+               lengths[i+1][j+1] = lengths[i][j] +1;
+            }
+            else {
+               int ml = MAX(lengths[i+1][j], lengths[i][j+1]);
+               lengths[i+1][j+1] = ml;
+            }
+        }
+    }
+
+    result = bufr+bufrlen;
+    *--result = '\0';
+    i = lena-1; j = lenb-1;
+    while ( (i>0) && (j>0) ) {
+        if (lengths[i][j] == lengths[i-1][j])  i -= 1;
+        else if (lengths[i][j] == lengths[i][j-1]) j-= 1;
+        else {
+//			assert( a[i-1] == b[j-1]);
+            *--result = a[i-1];
+            i-=1; j-=1;
+        }
+    }
+    free(la); free(lengths);
+    return strdup(result);
+}

rosalind/lcs.c~

@@ -0,0 +1,52 @@
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define MAX(A,B) (((A)>(B))? (A) : (B))
+
+char * lcs(const char *a,const char * b) {
+    int lena = strlen(a)+1;
+    int lenb = strlen(b)+1;
+
+    int bufrlen = 40;
+    char bufr[40], *result;
+
+    int i,j;
+    const char *x, *y;
+    int *la = calloc(lena*lenb, sizeof( int));
+    int  **lengths = malloc( lena*sizeof( int*));
+    for (i=0; i<lena; i++) lengths[i] = la + i*lenb;
+
+    for (i=0,x=a; *x; i++, x++) {
+        for (j=0,y=b; *y; j++,y++ ) {
+            if (*x == *y) {
+               lengths[i+1][j+1] = lengths[i][j] +1;
+            }
+            else {
+               int ml = MAX(lengths[i+1][j], lengths[i][j+1]);
+               lengths[i+1][j+1] = ml;
+            }
+        }
+    }
+
+    result = bufr+bufrlen;
+    *--result = '\0';
+    i = lena-1; j = lenb-1;
+    while ( (i>0) && (j>0) ) {
+        if (lengths[i][j] == lengths[i-1][j])  i -= 1;
+        else if (lengths[i][j] == lengths[i][j-1]) j-= 1;
+        else {
+//			assert( a[i-1] == b[j-1]);
+            *--result = a[i-1];
+            i-=1; j-=1;
+        }
+    }
+    free(la); free(lengths);
+    return strdup(result);
+}
+
+int main()
+{
+    printf("%s\n", lcs("thisisatest", "testing123testing")); // tsitest
+    return 0;
+}