text: var minCost = function(costs) {
      if(costs==null||costs.length==0){
          return 0;
      }
      for(var i=1; i<costs.length; i++){
          costs[i][0] += Math.min(costs[i-1][1],costs[i-1][2]);
          costs[i][1] += Math.min(costs[i-1][0],costs[i-1][2]);
          costs[i][2] += Math.min(costs[i-1][1],costs[i-1][0]);
      }
      var n = costs.length-1;
      return Math.min(Math.min(costs[n][0], costs[n][1]), costs[n][2]); 
  };