一道题:给定一整数序列A1，A2，...，An(可能有负数)，求A1到An的一个自序列，使得Ai到Aj的和最大。例如：整数序列-2，11，-4,13，-5,2，-5，-3,12，-9的最大子序列为21

最差的方法

```
var a = [-2,11,-4,13,-5,2,-5,-3,12,-9]
var b = new Set()

for(let n in a){
let nm = [];
for(let m = n;m<a.length;m++){
nm.push(a[m])
}
add(...nm)
}
function add(...nums){
nums.reduce((x,y)=>{
b.add(x+y);
return x+y;
})
}

Math.max(...b)

优化

```
var a = [-2,11,-4,13,-5,2,-5,-3,12,-9]
var b = new Set()

for(let n in a){
a.reduce((x,y)=>{
b.add(x+y);
return x+y;
})
a.shift()
}

Math.max(...b)

ES6

```
var a = [-2,11,-4,13,-5,2,-5,-3,12,-9]
var b = new Set()

new class res{
constructor(){
a.reduce((x,y)=>{
b.add(x+y);
return x+y;
})
a.shift()
if(a.length) new res()
}
}

Math.max(...b)

最优-动态规划

var a = [-2,11,-4,13,-5,2,-5,-3,12,-9]
function method(data){
var max = 0;
var m = data.length;
var sum = 0;
for(var i=0;i<m;i++){
sum+=data[i];
if(sum>max){
max=sum;
}else if(sum<0){
sum = 0;
}
}
return max;
}

method(a)