写了几天，搞定了贪吃蛇自动寻路……目前在20*20的格子上面可以稳定跑到100+分，200+的话……看运气吧o(╯□╰)o，总之算法还有很多可以修改的地方，而且UI部分还有部分没写的……
总结下：这次写的话主要算法用的是BFS，没有用A*算法，因为太复杂了，用JS实现感觉好难，所以暂时没有写……然后有两种策略，一种是吃到食物还能找到自己尾巴的话就直接去吃食物，如果发现找不到吃食物的路径OR吃了就会死那么就在头部附近找一个格子，格子满足两个条件：一个是到了这个格子之后可以找到去尾巴的路，第二个是这个格子离食物最远……其实策略主要是看了别人写的贪吃蛇算法搞出来的，可惜的是目前还是不能铺满整个格子orz……算法还得改啊哈哈哈o(╯□╰)o
代码如下【只放JS了】：

(function () {/*全局变量*/var g = {//获得or设置盒子的attributeattr : function (x, y, att, name) {var d = document.getElementById("box_" + x + "_" + y);if (d && name)d.setAttribute(att, name);else if (d)return d.getAttribute(att);},//随机创建点create : function (start, end) {return Math.floor(Math.random() * (end - start) + start);},addHandler: function (ele, type, handler) {if (ele.length === undefined) {if (ele.addEventListener) {ele.addEventListener(type, handler, false);}else if (ele.attachEvent) {ele.attachEvent("on" + type, handler);}else {ele['on' + type] = handler;}}else if (ele.length === 0) {console.log("The element is null!");return false;}else {for (var i = 0; i < ele.length; i ++) {if (ele[i].addEventListener) {ele[i].addEventListener(type, handler, false);}else if (ele[i].attachEvent) {ele[i].attachEvent("on" + type, handler);}else {ele[i]['on' + type] = handler;}}}},removeHandler: function(element, type, handler) {if (ele.length === undefined) {if (ele.removeEventListener)ele.removeEventListener(type, handler, false);else if (ele.detachEvent)ele.detachEvent("on" + type, handler);elseele['on' + type] = null;}else if (ele.length === 0) {return (console.log("the element is null"));}else {for (var i = 0; i < ele.length; i ++) {if (ele[i].removeEventListener)ele[i].removeEventListener(type, handler, false);else if (ele[i].detachEvent)ele[i].detachEvent("on" + type, handler);elseele[i]['on' + type] = null;}}},//运动方向direction : {left : 37,up : 38,right : 39,down : 40},//游戏设定setting : {size : 20,speed : 500,len : 3,func : null,direct : null}}/*Game构造器*/function Game (food) {this.snake = new Snake(food);this.food = food;var that = this;/*Snake构造器*/function Snake (food) {this.headX = 0;this.headY = 0;this.lastX = 0;this.lastY = 0;this.pos = [];this.f = 0;this.h = 0;this.food = food;};Snake.prototype.init = function () {this.headX = this.headY = this.lastX = this.lastY = 0;this.pos = [];}/*创建蛇*/Snake.prototype.create = function () {var x = g.create(g.setting.len, g.setting.size / 2),y = g.create(g.setting.len, g.setting.size / 2);//获得蛇的坐标for (var i = 0; i < g.setting.len; i ++) {y --;this.pos.push([x, y]);if (i === 0) {g.attr(x, y, "class", "snake head");g.attr(x, y, "touchable", "0");}else if (i === g.setting.len - 1){g.attr(x, y, "class", "snake tail")g.attr(x, y, "touchable", "1");}else {g.attr(x, y, "class", "snake");g.attr(x, y, "touchable", "0");}}this.headX = this.pos[0][0];this.headY = this.pos[0][1];this.lastX = this.pos[this.pos.length - 1][0];this.lastY = this.pos[this.pos.length - 1][1];};/*移动*/Snake.prototype.move = function () {this.headX = this.pos[0][0];this.headY = this.pos[0][1];this.lastX = this.pos[this.pos.length - 1][0];this.lastY = this.pos[this.pos.length - 1][1];g.attr(this.lastX, this.lastY, "class", " ");for (var i = this.pos.length - 1; i > 0; i --) {this.pos[i][0] = this.pos[i - 1][0];this.pos[i][1] = this.pos[i - 1][1];}if (command.length == 0)command.push(g.setting.direct);g.setting.direct = command.shift();command = [];switch (g.setting.direct) {case g.direction.up : this.headY    -= 1; break;case g.direction.down : this.headY  += 1; break;case g.direction.left : this.headX  -= 1; break;case g.direction.right : this.headX += 1; break;}this.pos[0][0] = this.headX;this.pos[0][1] = this.headY;this.lastX = this.pos[this.pos.length - 1][0];this.lastY = this.pos[this.pos.length - 1][1];for (var i = 0; i < this.pos.length; i ++) {g.attr(this.pos[i][0], this.pos[i][1], "class", "snake");g.attr(this.pos[i][0], this.pos[i][1], "touchable", "0");}g.attr(this.headX, this.headY, "class", "snake head");g.attr(this.lastX, this.lastY, "class", "snake tail");g.attr(this.lastX, this.lastY, "touchable", "1");var inside = g.attr(this.headX, this.headY, "inside");if (inside == "food") {this.lastX = this.pos[this.pos.length - 1][0];this.lastY = this.pos[this.pos.length - 1][1];if (this.lastX == this.pos[this.pos.length - 2][0]) {if (this.lastY - this.pos[this.pos.length - 2][1] == 1)this.pos.push([this.lastX, this.lastY + 1]);else if (this.pos[this.pos.length - 2][1] - this.lastY == 1)this.pos.push([this.lastX, this.lastY - 1]);}else if (this.lastY == this.pos[this.pos.length - 2][1]) {if (this.lastX - this.pos[this.pos.length - 2][0] == 1)this.pos.push([this.lastX + 1, this.lastY])else if (this.pos[this.pos.length - 2][0] - this.lastX == 1)this.pos.push([this.lastX - 1, this.lastY]);}g.attr(this.lastX, this.lastY, "class", "snake");g.attr(this.lastX, this.lastY, "touchable", "0");this.lastX = this.pos[this.pos.length - 1][0];this.lastY = this.pos[this.pos.length - 1][1];g.attr(this.lastX, this.lastY, "class", "snake tail");g.attr(this.lastX, this.lastY, "touchable", "1");score ++;this.food.create();document.getElementById("score").innerHTML = score;g.attr(this.headX, this.headY, "inside", " ");};//撞到自己或者墙，游戏结束for (var i = 1; i < this.pos.length; i ++) {if (this.headX == this.pos[i][0] && this.headY == this.pos[i][1]) {that.over();}else {continue;}}if (this.headX > (g.setting.size - 1) || this.headX < 0 || this.headY > (g.setting.size - 1) || this.headY < 0) {that.over();}};Snake.prototype.AIMode = function() {var head = [this.headX, this.headY],tail = [this.lastX, this.lastY],foodPos = this.food.pos,headPath = this.existPath(head, foodPos);if (headPath.length) {var test = this.fakemove(this.pos, headPath);if (test.length) {this.path(head, foodPos);}else {var fathest = this.farthest(head, foodPos, tail);if (fathest.length) {if (fathest[0] - head[0] > 0) {g.setting.direct = g.direction.right;}else if (fathest[0] - head[0] < 0) {g.setting.direct = g.direction.left;}else if (fathest[1] - head[1] > 0) {g.setting.direct = g.direction.down;}else if (fathest[1] - head[1] < 0) {g.setting.direct = g.direction.up;}}else {if (this.existPath(head, tail)) {this.path(head, tail);}else {this.path(head, foodPos);}}}}else {var fathest = this.farthest(head, foodPos, tail);if (fathest.length) {if (fathest[0] - head[0] > 0) {g.setting.direct = g.direction.right;}else if (fathest[0] - head[0] < 0) {g.setting.direct = g.direction.left;}else if (fathest[1] - head[1] > 0) {g.setting.direct = g.direction.down;}else if (fathest[1] - head[1] < 0) {g.setting.direct = g.direction.up;};}else {if (this.existPath(head, tail).length) {this.path(head, tail);}else {this.struggle(head);}}}};/* 算法JS实现 */Snake.prototype.path = function(sta, end) {var startX = sta[0], startY = sta[1], distance = this.existPath(sta, end);if (distance.length > 1) {if (distance[1][0] - startX > 0) {g.setting.direct = g.direction.right;}else if (distance[1][0] - startX < 0) {g.setting.direct = g.direction.left;}else if (distance[1][1] - startY > 0) {g.setting.direct = g.direction.down;}else if (distance[1][1] - startY < 0) {g.setting.direct = g.direction.up;}}}/* 贪吃蛇头部附近找个距离食物最远的有效点 */Snake.prototype.farthest = function(start, end, tail) {var startX = start[0], startY = start[1], endX = end[0], endY = end[1], que = [], distance = [];for (var i = -1; i <= 1; i ++) {if (i === 0) {continue;}else {if (startX + i < g.setting.size&& startX + i >= 0&& g.attr(startX + i, startY, "touchable") === '1'&& this.existPath([startX + i, startY], tail).length) {que.push([startX + i, startY])}if (startY + i < g.setting.size&& startY + i >= 0&& g.attr(startX, startY + i, "touchable") === '1'&& this.existPath([startX, startY + i], tail).length) {que.push([startX, startY + i])}}}for (var i = 0; i < que.length; i ++) {var dis = Math.sqrt(Math.pow(endX - que[i][0], 2) + Math.pow(endY - que[i][1], 2));distance.push([dis, que[i]]);}distance.sort(function(a, b) {return b[0] - a[0];})if (distance.length) {return distance[0][1];}else {return distance;}}/* 移动一条假蛇去吃食物以检查路径是否安全 */Snake.prototype.fakemove = function(pos, path) {var temp = [];if (path.length >= pos.length) {for (var i = path.length - 1; i >= path.length - pos.length; i --) {if (i === path.length - pos.length) {g.attr(path[i][0], path[i][1], "touchable", '1');}else {g.attr(path[i][0], path[i][1], "touchable", '0');}}for (var i = 0; i < pos.length; i ++) {g.attr(pos[i][0], pos[i][1], "touchable", "1");}temp = this.existPath(path[path.length - 1], path[path.length - pos.length]);}else {if (path.length > 2) {for (var i = pos.length - 1; i >= pos.length - path.length; i --) {g.attr(pos[i][0], pos[i][1], "touchable", "1");}for (var i = 0; i < path.length; i ++) {g.attr(path[i][0], path[i][1], "touchable", "0");}temp = this.existPath(path[path.length - 1], pos[pos.length - path.length]);}else {g.attr(pos[pos.length - 1][0], pos[pos.length - 1][1], "touchable", "1");for (var i = 0; i < path.length; i ++) {g.attr(path[i][0], path[i][1], "touchable", "0");}temp = this.existPath(path[path.length - 1], pos[pos.length - 1]);}}for (var i = path.length - 1; i >= 0; i --) {g.attr(path[i][0], path[i][1], "touchable", "1");}for (var i = pos.length - 2; i >= 0; i --) {g.attr(pos[i][0], pos[i][1], "touchable", "0");}g.attr(pos[pos.length - 1][0], pos[pos.length - 1][1], "touchable", "1");return temp;}/* BFS算法实现寻找路径 */Snake.prototype.existPath = function(start, end) {var visited = [], que = [], parent = [];var sta = start;for (var i = 0; i < g.setting.size; i ++) {visited[i] = [];parent[i] = [];for (var j = 0; j < g.setting.size; j ++) {visited[i][j] = false;parent[i][j] = [-1, -1];}}var tempque = [];tempque.push(start);if (start) {if (visited[start[0]])visited[start[0]][start[1]] = true;}while (tempque.length) {start = tempque.shift();var x = start[0], y = start[1];for (var i = -1; i <= 1; i ++) {if (i === 0) {continue;}else {if (x + i < g.setting.size&& x + i >= 0&& (g.attr(x + i, y, "touchable") === '1')&& !visited[x + i][y]) {tempque.push([x + i, y]);visited[x + i][y] = true;parent[x + i][y] = [x, y];if (x + i === end[0] && y === end[1]) {var temp = end;while (temp && temp[0] != -1) {que.unshift(temp);temp = parent[temp[0]][temp[1]];}}}if (y + i < g.setting.size&& y + i >= 0&& (g.attr(x, y + i, "touchable") === '1')&& !visited[x][y + i]) {tempque.push([x, y + i]);visited[x][y + i] = true;parent[x][y + i] = [x, y];if (x === end[0] && y + i === end[1]) {var temp = end;while (temp && temp[0] != -1) {que.unshift(temp);temp = parent[temp[0]][temp[1]];}}}}}}return que;}/* 实在没辙就只能就近做S形运动苟延残喘 */Snake.prototype.struggle = function(head) {var t = [-1, 1], x = head[0], y = head[1], que = [], die = 0;switch(g.setting.direct) {case g.direction.up:if (y - 1 < 0 || g.attr(x, y - 1, "class").indexOf("snake") != -1) {die = 1;}break;case g.direction.down:if (y + 1 >= g.setting.size || g.attr(x, y + 1, "class").indexOf("snake") != -1) {die = 1;}break;case g.direction.left:if (x - 1 < 0 || g.attr(x - 1, y, "class").indexOf("snake") != -1) {die = 1;}break;case g.direction.right:if (x + 1 >= g.setting.size || g.attr(x + 1, y, "class").indexOf("snake") != -1) {die = 1;}break;}if (die) {for (var i = 0; i < 2; i ++) {if (x + t[i] < g.setting.size&& x + t[i] >= 0&& g.attr(x + t[i], y, "class")&& g.attr(x + t[i], y, "class").indexOf("snake") == -1) {que.push([x + t[i], y]);}if (y + t[i] < g.setting.size&& y + t[i] >= 0&& g.attr(x, y + t[i], "class")&& g.attr(x, y + t[i], "class").indexOf("snake") == -1) {que.push([x, y + t[i]]);}}if (que.length) {if (que[0][0] - head[0] > 0) {g.setting.direct = g.direction.right;}else if (que[0][0] - head[0] < 0) {g.setting.direct = g.direction.left;}else if (que[0][1] - head[1] > 0) {g.setting.direct = g.direction.down;}else if (que[0][1] - head[1] < 0) {g.setting.direct = g.direction.up;}}}}};/*创建格子*/Game.prototype.pannel = function () {var t = [];t.push("<table>");for (var i = 0; i < g.setting.size; i ++) {t.push("<tr class = 'row' y = " + i + ">");for (var j = 0; j < g.setting.size; j ++) {t.push("<td id = 'box_" + j + "_" + i + "' inside = ' ' x = '" + j + "' y = '" + i + "' touchable=1></td>");}t.push("</tr>");}t.push("</table>");document.getElementById("pannel").innerHTML = t.join("");};/*初始化游戏*/Game.prototype.init = function () {score = 0;document.getElementById("score").innerHTML = score;this.snake.init();speed.disabled = start.disabled = false;if (g.setting.func) {window.clearInterval(g.setting.func);}for (var x = 0; x < g.setting.size; x ++) {for (var y = 0; y < g.setting.size; y ++) {g.attr(x, y, "class", " ");g.attr(x, y, "inside", " ");}}}/*游戏开始*/Game.prototype.start = function () {this.food.create();this.snake.create();g.setting.direct = g.direction.down;var that = this;g.setting.func = window.setInterval(function() {that.snake.AIMode();that.snake.move();}, g.setting.speed)//蛇移动//g.setting.func = window.setInterval(function() {//  snake.move();//}, g.setting.speed);}/*监听键盘*/Game.prototype.listen = function (e) {e = e || event;command.push(Math.abs(e.keyCode - g.setting.direct) != 2 && e.keyCode > 36 && e.keyCode < 41 ? e.keyCode : g.setting.direct);}/*游戏结束*/Game.prototype.over = function () {alert("game over XD!");this.init();};/*Food构造器*/function Food () {this.pos = [];};/*创建食物*/Food.prototype.create = function () {var that = this;var x = g.create(0, g.setting.size),y = g.create(0, g.setting.size);//检查是否与蛇的位置重合var c = g.attr(x, y, "class");if (c.indexOf("snake") != -1)return this.create();else {g.attr(x, y, "class", "food");g.attr(x, y, "inside", "food");}this.pos = [x, y];};var command = [], gameAi, foodAi, speed = document.getElementById("gameSpeed"), start = document.getElementById("start"), score = 0;foodAi = new Food();gameAi = new Game(foodAi);gameAi.pannel();gameAi.init();function gameStart() {this.disabled = true;g.setting.speed = speed.options[speed.selectedIndex].value;speed.disabled = true;gameAi.start();//window.onkeydown = game.listen;};function switchChange() {var cla = this.firstChild.className.split(" ");for (var i = 0; i < cla.length; i ++) {if (cla[i] == "switch-animate") {cla.splice(i, 1);break;}}cla = cla.join(" ");this.firstChild.className = cla;}function switchAnimate() {var cla = this.firstChild.className.split(" ");for (var i = 0; i < cla.length; i ++) {if (cla[i] == "switch-off") {cla.splice(i, 1, "switch-on");break;}else if (cla[i] == "switch-on") {cla[i] = "switch-off";break;}}cla.push("switch-animate");cla = cla.join(" ");this.firstChild.className = cla;}g.addHandler(start, "click", gameStart);g.addHandler(document.getElementsByClassName("switch"), 'mousedown', switchChange);g.addHandler(document.getElementsByClassName("switch"), 'mouseup', switchAnimate);
})()