24点牌算法实现

最近陪孩子玩24点牌，很能训练孩子的数学心算，要是早知道这种玩法就好了，我又写了一个JS实现的算法，挺有意思的

var inputs = [4,5,6,7];

var numbers = [{value:inputs[0]},{value:inputs[1]},{value:inputs[2]},{value:inputs[3]}];
var samplesAB = []

// a,b
for(var i=0;i<4;i++){
    for(var j=0;j<4;j++){
        var a = numbers[i];
        var b = numbers[j];
        if(a!=b){
            samplesAB.push({a:a,b:b})
        }
    }
}

var samplesABC = [];
// a,b,c
for(var i=0;i<samplesAB.length;i++){
    for(var j=0;j<4;j++){
        var ab = samplesAB[i];
        var c = numbers[j];
        if(ab.a!=c && ab.b != c){
            samplesABC.push({...ab,c:c})
        }
    }
}

var samples = [];
// a,b,c
for(var i=0;i<samplesABC.length;i++){
    for(var j=0;j<4;j++){
        var abc = samplesABC[i];
        var d = numbers[j];
        if(abc.a!=d && abc.b!=d && abc.c!=d){
            samples.push({...abc,d:d})
        }
    }
}

//+=*、
var sampleOp1 = [];
for(var i =0;i<samples.length;i++){
    var sample = samples[i];

    sampleOp1.push({...sample,op1:"+"});
    sampleOp1.push({...sample,op1:"-"});
    sampleOp1.push({...sample,op1:"*"});
    sampleOp1.push({...sample,op1:"/"});
}

var sampleOp2 = [];
for(var i =0;i<sampleOp1.length;i++){
    var sample = sampleOp1[i];

    sampleOp2.push({...sample,op2:"+"});
    sampleOp2.push({...sample,op2:"-"});
    sampleOp2.push({...sample,op2:"*"});
    sampleOp2.push({...sample,op2:"/"});
}

var sampleOp3 = [];
for(var i =0;i<sampleOp2.length;i++){
    var sample = sampleOp2[i];

    sampleOp3.push({...sample,op3:"+"});
    sampleOp3.push({...sample,op3:"-"});
    sampleOp3.push({...sample,op3:"*"});
    sampleOp3.push({...sample,op3:"/"});
}

//操作符优先级
var expressions = [];
for(var i =0;i<sampleOp3.length;i++){
    var sample = sampleOp3[i];

    var a = sample.a.value;
    var b = sample.b.value;
    var c = sample.c.value;
    var d = sample.d.value;
    var op1 = sample.op1;
    var op2 = sample.op2;
    var op3 = sample.op3;

    expressions.push(a + op1 + b + op2 + c + op3 + d);

    expressions.push("("+a + op1 + b +")" + op2 + c + op3 +d );
    expressions.push(a +  op1 +"("+ b + op2 + c+")" + op3+d);
    expressions.push(a + op1 + b + op2 +"("+ c + op3 + d+")");
    expressions.push("("+a + op1 + b +")" + op2 +"("+ c + op3 + d+")");

    // expressions.push("("+a + op1 + b + op2 + c+")" + op3 + d);
    expressions.push("(("+a + op1 + b+")" + op2 + c+")" + op3 + d);
    expressions.push("("+a + op1 +"("+ b + op2 + c+"))" + op3 + d);

    // expressions.push(a + op1 +"("+ b + op2 + c + op3 + d+")");
    expressions.push(a + op1 +"(("+ b + op2 + c +")" + op3 + d+")");
    expressions.push(a + op1 +"("+ b + op2 +"("+ c + op3 + d+"))");
    
}

var index = 1000;
for(var i=0;i<expressions.length;i++){
    var expression = expressions[i];
    var value = eval(expression);
    if(value==24){
        console.log(index.toString().substr(1) +" : 24 = " +expression);
        index++;
    }
}