Given two strings , find if first string is a subsequence of second | Returns true if str1 [ ] is a subsequence of str2 [ ] . m is length of str1 and n is length of str2 ; Base Cases ; If last characters of two strings are matching ; If last characters are not matching ; Driver Code
< ? php function isSubSequence ( $ str1 , $ str2 , $ m , $ n ) { if ( $ m == 0 ) return true ; if ( $ n == 0 ) return false ; if ( $ str1 [ $ m - 1 ] == $ str2 [ $ n - 1 ] ) return isSubSequence ( $ str1 , $ str2 , $ m - 1 , $ n - 1 ) ; return isSubSequence ( $ str1 , $ str2 , $ m , $ n - 1 ) ; } $ str1 = " gksrek " ; $ str2 = " geeksforgeeks " ; $ m = strlen ( $ str1 ) ; $ n = strlen ( $ str2 ) ; $ t = isSubSequence ( $ str1 , $ str2 , $ m , $ n ) ? " Yes ▁ " : " No " ; if ( $ t = true ) echo " Yes " ; else echo " No " ; ? >