第一遍：最大的值一定 到最后面了
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<script>
var arr = [20,13,15,60,12]
console.log(arr.length)//5 对比次数为4
for (var i = 0;i<arr.length-1; i++){//4
if(arr[i]>arr[i+1]){
var temp = arr[i]
arr[i] = arr[i+1]
arr[i+1] = temp
}
}
console.log(arr)// [ 13, 15, 20, 12, 60 ]
for (var i = 0;i<arr.length-1-1; i++){//3 在arr.length开始减的
if(arr[i]>arr[i+1]){
var temp = arr[i]
arr[i] = arr[i+1]
arr[i+1] = temp
}
}
console.log(arr)// [ 13, 15, 12, 20, 60 ]
for (var i = 0;i<arr.length-1-1-1; i++){//2
if(arr[i]>arr[i+1]){
var temp = arr[i]
arr[i] = arr[i+1]
arr[i+1] = temp
}
}
console.log(arr)//[ 13, 12, 15, 20, 60 ]
// console.log(arr.length-1-1-1-1) = 1
for (var i = 0;i<arr.length-1-1-1-1; i++){ //1
if(arr[i]>arr[i+1]){
var temp = arr[i]
arr[i] = arr[i+1]
arr[i+1] = temp
}
}
console.log(arr)//[ 12, 13, 15, 20, 60 ]
//j=1的时候停止
for(var j = arr.length-1;j>0;j--){//减3次
for (var i = 0;i<arr.length-1; i++){//4
if(arr[i]>arr[i+1]){
var temp = arr[i]
arr[i] = arr[i+1]
arr[i+1] = temp
}
}
}
console.log(arr)//[ 12, 13, 15, 20, 60 ]
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