看到一个小学四年级的数学题，说是一共4个人过桥，分别单独过桥用时3,4,6,9分钟，该桥每次只能过两个人，且每次过去之后必须要一个人回去接人，问四个人全部过去的最短时间。
真实题目确实很长，我不知道小学生遇到这个问题能否耐心读完读懂该问题。
所以我觉得题目确实蛮有意思的，有点脑筋急转弯的感觉。
如果静下心来解决，用排除法也能很快得到答案。
另外用Javascript穷尽法也能得到答案，网上还有人问js怎么写。
能力有限，用的比较死板的解决办法，应该有大神有更好的解决办法。
/// <reference path="jquery-1.10.2.js" />
$(document).ready(function () {
$('#CrossBridge').html();
HowToCrossBridge(3, 4, 6, 9);
});
/**
//console.log("第一次过桥由" + firstGo1 + "和" + firstGo2 + "过,共计" + firstGo2 + "分钟");
//document.writeln("第一次过桥由" + firstGo1 + "和" + firstGo2 + "过,共计" + firstGo2 + "分钟");
知识点:
1.数组的copy 注意区分深拷贝和浅拷贝
array.slice(0)以及array.concat()
2.数组的remove和push以及sort
**/
function HowToCrossBridge(a, b, c, d) {
var totalTime1 = 0;
var breakFlag = true;
var str1 = "";
var count = 0;
var minTime = 0;
var minStr = "";
//while (breakFlag) {
//totalTime1 = 0;
var waitingCross = [a, b, c, d];
var hadCrossed = new Array();
waitingCross = waitingCross.sort(function (a, b) { return a - b });//按顺序从小到大排序
//第一次过桥(过去2人，剩余2人)
for (var i = 0; i < 4; i++) {
for (var j = i + 1; j < 4; j++) {
//count += 1;
totalTime1 = 0;
var hadCrossed1 = hadCrossed.concat();
var waitingCross1 = waitingCross.concat();
var firstGo1 = waitingCross1[i];
var firstGo2 = waitingCross1[j];
totalTime1 = totalTime1 + firstGo2;
str1 = "<p>第一次过桥由" + firstGo1 + "和" + firstGo2 + "过,共计<fond style='color:red'>" + firstGo2 + "</fond>分钟,合计<fond style='color:red'>" + totalTime1 + "</fond>分钟</p>";
//移除等待过桥人员
waitingCross1.remove(firstGo1);
waitingCross1.remove(firstGo2);
waitingCross1.sort(function (a, b) { return a - b });
//添加已过桥人员
hadCrossed1 = [firstGo1, firstGo2];
hadCrossed1.sort(function (a, b) { return a - b });
str1 += "<p>第一次过桥后 hadCrossed=" + hadCrossed1.join() + " waitingCross=" + waitingCross1.join() + "</p>";
//第二次返回(过去1人，剩余3人)
for (var k = 0; k < 2; k++) {
//count += 1;
var hadCrossed2 = hadCrossed1.concat();
var waitingCross2 = waitingCross1.concat();
var str2 = str1;
var totalTime2 = totalTime1;
var secondBack = hadCrossed2[k];
totalTime2 = totalTime2 + secondBack;
str2 += "<p>第二次返回由" + secondBack + "过,共计<fond style='color:red'>" + secondBack + "</fond>分钟,合计<fond style='color:red'>" + totalTime2 + "</fond>分钟</p>";
//添加等待过桥人员
waitingCross2.push(secondBack);
waitingCross2.sort(function (a, b) { return a - b });
//移除已过桥人员
hadCrossed2.remove(secondBack);
hadCrossed2.sort(function (a, b) { return a - b });
str2 += "<p>第二次返回后 hadCrossed=" + hadCrossed2.join() + " waitingCross=" + waitingCross2.join() + "</p>";
//第三次过桥(过去3人，剩余1人)
for (var m = 0; m < 3; m++) {
for (var n = m + 1; n < 3; n++) {
//count += 1;
var str3 = str2;
var hadCrossed3 = hadCrossed2.concat();
var waitingCross3 = waitingCross2.concat();
var totalTime3 = totalTime2;
var thirdGo1 = waitingCross3[m];
var thirdGo2 = waitingCross3[n];
totalTime3 = totalTime3 + thirdGo2;
str3 += "<p>第三次过桥由" + thirdGo1 + "和" + thirdGo2 + "过,共计<fond style='color:red'>" + thirdGo2 + "</fond>分钟,合计<fond style='color:red'>" + totalTime3 + "</fond>分钟</p>";
//移除
waitingCross3.remove(thirdGo1);
waitingCross3.remove(thirdGo2);
waitingCross3.sort(function (a, b) { return a - b });
hadCrossed3.push(thirdGo1);
hadCrossed3.push(thirdGo2);
hadCrossed3.sort(function (a, b) { return a - b });
str3 += "<p>第三次过桥后 hadCrossed=" + hadCrossed3.join() + " waitingCross=" + waitingCross3.join() + "</p>";
//第四次返回(过去2人，剩余2人)
for (var l = 0; l < 2; l++) {
count += 1;
var hadCrossed4 = hadCrossed3.concat();
var waitingCross4 = waitingCross3.concat();
var str4 = str3;
var totalTime4 = totalTime3;
var fouthBack = hadCrossed4[l];
totalTime4 = totalTime4 + fouthBack;
str4 += "<p>第四次返回由" + fouthBack + "过,共计<fond style='color:red'>" + fouthBack + "</fond>分钟,合计<fond style='color:red'>" + totalTime4 + "</fond>分钟</p>";
//添加
waitingCross4.push(fouthBack);
waitingCross4.sort(function (a, b) { return a - b });
//移除
hadCrossed4.remove(fouthBack);
hadCrossed4.sort(function (a, b) { return a - b });
str4 += "<p>第四次返回后 hadCrossed=" + hadCrossed4.join() + " waitingCross=" + waitingCross4.join() + "</p>";
//第五次过桥（全部通过）
var hadCrossed5 = hadCrossed4.concat();
var waitingCross5 = waitingCross4.concat();
var totalTime5 = totalTime4;
var fifthGo1 = waitingCross5[0];
var fifthGo2 = waitingCross5[1];
totalTime5 = totalTime5 + fifthGo2;
str4 += "<p>第五次过桥由" + fifthGo1 + "和" + fifthGo2 + "过,共计<fond style='color:red'>" + fifthGo2 + "</fond>分钟,合计<fond style='color:red'>" + totalTime5 + "</fond>分钟</p>";
//添加
waitingCross5.remove(fifthGo1);
waitingCross5.remove(fifthGo2);
waitingCross5.sort(function (a, b) { return a - b });
//移除
hadCrossed5.push(fifthGo1);
hadCrossed5.push(fifthGo2);
hadCrossed5.sort(function (a, b) { return a - b });
str4 += "<p>第五次过桥后 hadCrossed=" + hadCrossed5.join() + " waitingCross=" + waitingCross5.join() + "</p>";
str4 += "<p><fond style='color:red'>本方案共计" + totalTime5 + "分钟</fond></p>";
var str5 = "方案" + count + str4;
str5 += "<p>==================================================================</p>";
$('#CrossBridge').append(str5);
if (minTime > 0) {
if (totalTime5 < minTime) {
minStr = str5;
}
}
else {
minTime = totalTime5;
minStr = str5;
}
}
}
}
}
}
}
//}
$('#CrossBridge').append("<p>/********************************************最短时间方案为**************************************************************/</p>");
$('#CrossBridge').append(minStr);
}
/*
数组中随机取几个元素
var items = ['1','2','4','5','6','7','8','9','10'];
console.log( getRandomArrayElements(items, 4) );
数组中随机获取一个元素
var item = items[Math.floor(Math.random()*items.length)];
*/
function getRandomArrayElements(arr, count) {
var shuffled = arr.slice(0), i = arr.length, min = i - count, temp, index;
while (i-- > min) {
index = Math.floor((i + 1) * Math.random());
temp = shuffled[index];
shuffled[index] = shuffled[i];
shuffled[i] = temp;
}
return shuffled.slice(min);
}
Array.prototype.indexOf = function (val) {
for (var i = 0; i < this.length; i++) {
if (this[i] == val)
return i;
}
return -1;
}
Array.prototype.remove = function (val) {
var index = this.indexOf(val);
if (index > -1) {
this.splice(index, 1);
}
}
