give string s1 s2 s3 find s3 form interleave s1 s2an interleaving string s t configuration s t divide n m substring respectively that s s1 s2 snt t1 t2 tmn m 1the interleaving s1 t1 s2 t2 s3 t3 t1 s1 t2 s2 t3 s3 Note b concatenation string b example 1input s1 aabcc s2 dbbca s3 aadbbcbcacoutput trueExplanation one way obtain s3 isSplit s1 s1 aa bc c s2 s2 dbbc aInterleaving split aa dbbc bc c aadbbcbcacsince s3 obtain interleaving s1 s2 return trueexample 2input s1 aabcc s2 dbbca s3 aadbbbacccOutput falseexplanation Notice impossible interleave s2 string obtain s3example 3input s1 s2 s3 Output true constraints0 s1length s2length 1000 s3length 200s1 s2 s3 consist lowercase English letter Follow could solve os2length additional memory space