Merge pull request #539 from SOUHARDYAADHIKARY1999/master

longest common subsequence added

Author: probot-auto-merge[bot]

C/lcs.c

@@ -0,0 +1,82 @@
+#include<stdio.h>
+#include<stdlib.h>
+#include<string.h>
+void printMat(int** ar,int n,int m)
+{
+    int i = 0,j = 0;
+    for(i =0 ; i< n ;i++)
+    {
+        for(j = 0; j< m; j++)
+        {
+            printf("%d\t", ar[i][j]);
+        }
+        printf("\n" );
+    }
+}
+void LCSPrint(char* X, int** dir, int n, int m)
+{
+  //printf("%d-%d-%d\n",dir[n][m],n,m );
+    if(dir[n][m]==1)
+    {
+        LCSPrint(X,dir,n-1,m-1);
+        printf("%c",X[m-1] );
+    }
+    else if(dir[n][m] == 2)
+    {
+        LCSPrint(X, dir, n-1,m);
+    }
+    else if(dir[n][m]==3)
+    {
+        LCSPrint(X,dir,n,m-1);
+    }
+}
+void LCS(char* p1, char* p2, int n1, int n2)
+{
+    int i = 0, j= 0;
+    n1++;
+    n2++;//Important
+    int **ar = (int**)calloc(n1,sizeof(int*));
+    int **dir = (int**)calloc(n1,sizeof(int*));
+    for(i = 0; i< n1+1; i++)
+    {
+        ar[i] = (int*)calloc(n2,sizeof(int));
+        dir[i] = (int*)calloc(n2,sizeof(int));
+    }
+    for(i = 1; i< n1; i++)
+    {
+        for(j = 1;j< n2; j++)
+        {
+            if(p1[i-1] == p2[j-1])
+            {
+                ar[i][j] = ar[i-1][j-1]+1;
+                dir[i][j] = 1;
+            }
+            else
+            {
+                if(ar[i-1][j] >= ar[i][j-1])
+                {
+                    ar[i][j] = ar[i-1][j];
+                    dir[i][j] = 2;
+                }
+                else
+                {
+                    ar[i][j] = ar[i][j-1];
+                    dir[i][j] = 3;
+                }
+            }
+        }
+    }
+    printMat(ar,n1,n2);
+    printf("=========\n" );
+    printMat(dir,n1,n2);
+    LCSPrint(p2,dir,n1-1,n2-1);
+}
+int main()
+{
+    char X[] = "ABCBDAB";
+    char Y[] = "BDCABA";
+
+    int m = strlen(X);
+    int n = strlen(Y);
+    LCS(X,Y,m,n);
+}