我一直在尝试在 JS 中制作动画冒泡排序，但每次我运行代码时，它都会从随机顺序变为即时排序。每次我交换颜色代码数组中的两个东西后，如何让它重新绘制并停止一段时间。
<html>
<body>
<canvas id="myCanvas" width="300" height="700" style="border:1px solid #d3d3d3;">
</canvas>
<script>
function swap(nums, pos1,pos2) {
var a = nums[pos1];
nums[pos1] = nums[pos2];
nums[pos2] = a;
}
function shuffle(nums) {
for (var i = 0; i < 1000; i++) {
var num1 = Math.floor((Math.random())*26);
var num2 = Math.floor((Math.random())*26);
swap(nums,num1,num2);
}
}
function sleep(seconds)
{
var e = new Date().getTime() + (seconds * 1000);
while (new Date().getTime() <= e) {}
}
function drawIt(nums) {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
for (var i = 0; i < nums.length; i++) {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.rect(10, i * 20 + 10, 50, 20);
ctx.stroke();
ctx.fillStyle = "rgba(" + nums[i] + ", " + nums[i] + ", " + nums[i] + ", 1)";
ctx.fill();
}
}
var nums = new Array();
for (var i = 0; i<=250; i+=10) {
nums[i/10] = i;
}
shuffle(nums);
drawIt(nums);
for (var i = 0; i < nums.length-1; i++) {
for (var j = i+1; j < nums.length; j++) {
if (nums[i] > nums[j]) {
swap(nums, i,j);
drawIt(nums);
}
}
}
</script>
</body>
</html>我尝试使用 setTimeout() 但没有任何效果。
编辑:
这是您的意思吗，因为这仍然无法正常工作。
<html>
<body>
<canvas id="myCanvas" width="300" height="800" style="border:1px solid #d3d3d3;">
</canvas>
<script>
function swap(nums, pos1,pos2) {
var a = nums[pos1];
nums[pos1] = nums[pos2];
nums[pos2] = a;
}
function shuffle(nums) {
for (var i = 0; i < 1000; i++) {
var num1 = Math.floor((Math.random())*26);
var num2 = Math.floor((Math.random())*26);
swap(nums,num1,num2);
}
}
var counter1 = 0;
var counter2 = 1;
function drawIt(nums) {
if (nums[counter1] > nums[counter2]) {
swap(nums, counter1,counter2);
}
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
for (var i = 0; i < nums.length; i++) {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.lineWidth = "1";
ctx.strokeStyle = "rgba(" + nums[i] + ", " + nums[i] + ", " + nums[i] + ", 1)";
ctx.rect(10, i * 15 + 10, 50, 15);
ctx.stroke();
ctx.beginPath();
ctx.rect(10, i * 15 + 10, 50, 15);
ctx.stroke();
ctx.fillStyle = "rgba(" + nums[i] + ", " + nums[i] + ", " + nums[i] + ", 1)";
ctx.fill();
}
if (counter2 < nums.length) {
counter2++;
}
else {
counter1++;
counter2 = counter1+1;
}
}
var nums = new Array();
for (var i = 0; i<=250; i+=5) {
nums[i/5] = i;
}
shuffle(nums);
drawIt(nums);
for (var i = 0; i < (nums.length*(nums.length-1)) / 2; i++) {
setTimeout(drawIt(nums), 2000);
}
</script>
</body>
</html>最佳答案
不幸的是，当您的线程仍在运行时，无法强制绘制或更新 DOM。解决这个问题的方法是使您的排序算法可重入，以便可以从计时器或通过 setTimeout 调用它。每次触发计时器时，您都会执行一次排序迭代，然后绘制结果。
在通过可视化研究算法时，有时这有点烦人，因为如果不修改算法就无法实现逐步可视化。
编辑:添加了实现“可重入”排序的工作代码片段。
<html>
<body>
<canvas id="myCanvas" width="300" height="700" style="border:1px solid #d3d3d3;">
</canvas>
<script>
function swap(nums, pos1,pos2) {
var a = nums[pos1];
nums[pos1] = nums[pos2];
nums[pos2] = a;
}
function shuffle(nums) {
for (var i = 0; i < 1000; i++) {
var num1 = Math.floor((Math.random())*26);
var num2 = Math.floor((Math.random())*26);
swap(nums,num1,num2);
}
}
function sleep(seconds)
{
var e = new Date().getTime() + (seconds * 1000);
while (new Date().getTime() <= e) {}
}
function drawIt(nums) {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
for (var i = 0; i < nums.length; i++) {
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.rect(10, i * 20 + 10, 50, 20);
ctx.stroke();
ctx.fillStyle = "rgba(" + nums[i] + ", " + nums[i] + ", " + nums[i] + ", 1)";
ctx.fill();
}
}
var nums = new Array();
for (var i = 0; i<=250; i+=10) {
nums[i/10] = i;
}
shuffle(nums);
function sort()
{
var i=0;
var j=0;
var sortComplete=false;
var reentrantSort = function()
{
if (nums[i] > nums[j]){
swap(nums, i, j);
drawIt(nums)
}
j++;
if (j == nums.length){
j=0;i++;
if (i == nums.length ) {
i=0;j=0;
sortComplete=true; //Sorting is done
}
}
if (!sortComplete){ // If sort still not complete
setTimeout(reentrantSort,40); // Run next iteration in 40 ms.
}
};
reentrantSort();
}
sort();
</script>
</body>
</html>关于javascript - 在排序函数执行期间强制重绘以动画化步骤，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44252193/