give m x n grid character board string word return true word exist gridthe word construct letter sequentially adjacent cell adjacent cell horizontally vertically neighbor the letter cell Example 1input board ABCESFCSADEE word ABCCEDOutput trueExample 2Input board ABCESFCSADEE word SEEOutput trueExample 3input board ABCESFCSADEE word ABCBOutput false Constraintsm boardlengthn boardilength1 m n 61 wordlength 15board word consist lowercase uppercase English letter Follow could use search prune solution fast large board