func gridSearch(G: [String], P: [String]) -> String {
    // Write your code here
    
    var pIndex: Int = 0
    var gIndex: Int = 0
    var prevIndex: Int = -1
    
    var set = Set<Character>()
    
    while(gIndex <= G.count - 1) {
        if let ranged = G[gIndex].range(of: P[pIndex], options: .regularExpression) {
            let index: Int = G[gIndex].distance(from: G[gIndex].startIndex, to: ranged.lowerBound)
                   
            if prevIndex != -1 && prevIndex != index { 
                let squeezed: String = G[gIndex - 1].filter{ set.insert($0).inserted }
                if squeezed.count != 1 {
                    pIndex = 0
                    prevIndex = -1
                    continue
                }
             }
            if pIndex == P.count - 1 { break } 
            if pIndex < P.count - 1 { pIndex += 1 } 
            if prevIndex == -1 { prevIndex = index }
            
        } else if (pIndex != 0) {
            pIndex = 0 
            continue 
        }

        gIndex += 1
    }
        
    return pIndex == P.count - 1 ? "YES" : "NO"
}