如何在 Java 中使用 for 循环编写最短路径问题

Question

我创建了一个动作数组，每个动作都有一个成本。在此之后，我实施了一个 for 循环以找到成本最低的操作。其次，我必须检查先决条件，看看哪些操作是可能的。

//Actions
static Action loadPlaneP1 = new Action("loadPlaneP1",pkg1Location[1], pkg2Location[0], truckLocation[0], planeLocation[0], cityLocation[0], 30);
static Action loadPlaneP2 = new Action("loadPlaneP2", pkg1Location[0], pkg2Location[1], truckLocation[0], planeLocation[0], cityLocation[0], 40);
static Action fly = new Action("fly",pkg1Location[1], pkg2Location[1], truckLocation[0], planeLocation[1], cityLocation[0], 100);
static Action unloadPlaneP1 = new Action("unloadPlaneP1",pkg1Location[2], pkg2Location[1], truckLocation[0], planeLocation[2], cityLocation[1], 50);
static Action unloadPlaneP2 = new Action("unloadPlaneP2",pkg1Location[1], pkg2Location[2], truckLocation[0], planeLocation[2], cityLocation[1], 55);
static Action loadTruckP1 = new Action("loadTruckP1",pkg1Location[3], pkg2Location[2], truckLocation[0], planeLocation[2], cityLocation[1], 60);
static Action loadTruckP2 = new Action("loadTruckP2",pkg1Location[2], pkg2Location[3], truckLocation[0], planeLocation[2], cityLocation[1], 10);
static Action drive = new Action("drive",pkg1Location[3], pkg2Location[3], truckLocation[1], planeLocation[2], cityLocation[1], 70);
static Action unloadTruckP1 = new Action("unloadTruckP1", pkg1Location[5], pkg2Location[5], truckLocation[2], planeLocation[2], cityLocation[1], 40);
static Action unloadTruckP2 = new Action("unloadTruckP2",pkg1Location[4], pkg2Location[4], truckLocation[3], planeLocation[2], cityLocation[1], 43);

//Array
static Action[] acts = { loadPlaneP1, loadPlaneP2, fly, unloadPlaneP1, unloadPlaneP2, loadTruckP1, loadTruckP2, drive, unloadTruckP1, unloadTruckP2 };

问题出在主要逻辑上，因为当我打印动作名称和获得的成本时，显示的是loadPlaneP1（成本较低的那个）但是我通过[=15=得到的参数]是unloadTruckP2（数组最后一个）的参数。

此外，如果我将成本更改为将另一个操作成本设置为最低，则逻辑不起作用。

//Main logic
System.out.println("Old state parameters are " + "pkg1Location: " + state.getStateParameter1() + " pkg2Location: " + state.getStateParameter2() + " truckLocation: "+ state.getStateParameter3() + " planeLocation: " + state.getStateParameter4() + " cityLocation:"+ state.getStateParameter5());

for(int i = 0; acts[i].getActionCost() == getMinValue(costs); i++) {
    System.out.println("PRE The first parameter is : " + acts[i].getActParameter1() + acts[i].name);

    if(acts[i].getActParameter1() == "plane") {
        System.out.println("POST The first parameter is : " + acts[i].getActParameter1());
        System.out.println("Precondition satysfied" + " with action name: " + acts[i].name);

        if(acts[i].getActParameter1() != state.getStateParameter1()) {
            state.setStateParameter1(acts[i].getActParameter1());
        }

        if(acts[i].getActParameter2() != state.getStateParameter2()) {
            state.setStateParameter2(acts[i].getActParameter2());
        }

        if(acts[i].getActParameter3() != state.getStateParameter3()) {
            state.setStateParameter3(acts[i].getActParameter3());
        }

        if(acts[i].getActParameter4() != state.getStateParameter4()) {
            state.setStateParameter4(acts[i].getActParameter4());
        }

        if(acts[i].getActParameter5() != state.getStateParameter5()) {
            state.setStateParameter5(acts[i].getActParameter5());
        }
    }

    Node child = new Node(state, startNode, acts[i].getActionCost());

    /*  List<Action> removeList = new ArrayList<Action>(Arrays.asList(acts));
        removeList.remove(Arrays.asList(i));
        acts = removeList.toArray(acts);*/

    //nextAction = acts[i];
    System.out.println("Costs array: "+  Arrays.toString(costs));
    System.out.println("ActionID" +" " +  i);
    System.out.println("The action choosen is " + acts[i].name + acts[i].actionCost + acts[i].getActParameter1());
    System.out.println("State parameters updated are " + "pkg1Location: " + state.getStateParameter1() + " pkg2Location: " + state.getStateParameter2() + " truckLocation: "+ state.getStateParameter3() + " planeLocation: " + state.getStateParameter4() + " cityLocation:"+ state.getStateParameter5());
    };

}

我收到的输出是

Old state parameters are pkg1Location: lhr pkg2Location: lhr truckLocation: cdg planeLocation: lhr cityLocation:london
PRE The first parameter is : southloadPlaneP1
POST The first parameter is : south
Precondition satysfied with action name: loadPlaneP1
Costs array: [30, 40, 100, 50, 55, 60, 70, 70, 40]
ActionID 0
The action choosen is loadPlaneP130south
State parameters updated are pkg1Location: south pkg2Location: south truckLocation: south planeLocation: cdg cityLocation:paris

所以条件不满足，因为我从getActParameter1()得到的参数和loadPlaneP1得到的参数不一样。

为什么会这样？

Answer 1

我在您的代码中看到的一个问题是 for 循环条件，如果实际成本不是最小成本，它会停止循环。因此，如果在第一次迭代中实际成本不等于最小成本，则永远不会迭代 for 循环。我没有试图找出你在 for 循环中做了什么。可能还有更多错误。

for( int i = 0; i < acts.length -1; i++ ) 
{
   if ( acts[i].getActionCost( ) == getMinValue( costs ) )
   { 
     System.out.println( "PRE The first parameter is : " +  
                        acts[i].getActParameter1() + acts[i].name );

     if ( acts[i].getActParameter1() == "plane" ) 
     {
        System.out.println( "POST The first parameter is : " + 
                            acts[i].getActParameter1() );
        System.out.println( "Precondition satysfied with action name: " + 
                            acts[i].name );

        if ( acts[i].getActParameter1() != state.getStateParameter1() ) 
        {
          state.setStateParameter1( acts[i].getActParameter1() );
        }

        if(acts[i].getActParameter2() != state.getStateParameter2()) 
        {
          state.setStateParameter2( acts[i].getActParameter2() );
        }

        if( acts[i].getActParameter3() != state.getStateParameter3() ) 
        {
          state.setStateParameter3( acts[i].getActParameter3() );
        }

        if( acts[i].getActParameter4() != state.getStateParameter4() ) 
        {
          state.setStateParameter4( acts[i].getActParameter4() );
        }

        if( acts[i].getActParameter5() != state.getStateParameter5() ) 
        {
          state.setStateParameter5( acts[i].getActParameter5() );
        }
    }

    Node child = new Node(state, startNode, acts[i].getActionCost());

    System.out.println( "Costs array: "+  Arrays.toString( costs ) );
    System.out.println( "ActionID" +" " +  i );
    System.out.println( "The action choosen is " + acts[i].name + 
                        acts[i].actionCost + acts[i].getActParameter1() );
    System.out.println( "State parameters updated are " + "pkg1Location: " + 
                        state.getStateParameter1() + " pkg2Location: " +
                        state.getStateParameter2() + " truckLocation: "+ 
                        state.getStateParameter3() + " planeLocation: " + 
                        state.getStateParameter4() + " cityLocation:"+ 
                        state.getStateParameter5());
  }
}

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