农夫过河程序。农夫载狼、羊、菜过一条河，每次只允许农夫和其中最多一样过河。若无农夫看管，狼若和羊在一起时，狼会吃掉羊；若羊和菜一起时，羊会吃掉菜。使农夫、狼羊和菜安全到达河的对岸。-The farmer across the river program. Farmer set the wolf, sheep, vegetables across a river, each of which allows only up to the farmer and the same river. Without the farmer custody, if the wolf and sheep together, the wolf will eat the sheep　if sheep and vegetables together, the sheep will eat the food. The farmer, the wolf and the sheep across the river to reach food security.