Swift 最大子数组

来源：互联网发布：景观大数据软件课程编辑：程序博客网时间：2024/06/07 05:54

用递归吧，分治策略，求最大子数组

//: Playground - noun: a place where people can playimport UIKitvar str = "Hello, playground"var A = [13,-3,-25,20,-3,-16,-23,18,20,-7,12,-5,-22,15,-4,7]for i in 0..<A.count {    print(A[i])    }func FINDMAXCROSSINGSUBARRAY(A:[Int],low:Int,mid:Int,high:Int)->(maxleft:Int,maxright:Int,lr:Int){    var sum = 0    var maxleft = 0    var maxright = 0    var left_sum = -1000;    for i in stride(from: mid, through: low, by: -1)  {        sum = A[i] + sum        if(sum > left_sum)        {            left_sum = sum            maxleft = i        }            }    var right_sum = -1000    sum = 0    for j in mid+1...high    {        sum += A[j]        if(sum > right_sum)        {            right_sum = sum            maxright = j        }    }        return(maxleft,maxright,left_sum+right_sum)    }func FINDMAXIMUMSUBARRAY(A:[Int],low:Int,high:Int) ->(l:Int,h:Int,zhi:Int){    if (high == low) {        return (low,high,A[low])    }    else {        let mid = (low+high)/2        let a = FINDMAXIMUMSUBARRAY(A: A, low: low, high: mid)            let b = FINDMAXIMUMSUBARRAY(A: A, low: mid+1, high: high)        let c = FINDMAXCROSSINGSUBARRAY(A: A, low: low, mid: mid, high: high)        if(a.zhi >= b.zhi && a.zhi >= c.lr)        {return (a.l,a.h,a.zhi)}        else if (b.zhi >= a.zhi && b.zhi >= c.lr)        { return (a.l,b.h,b.zhi)}        else {return (c.maxleft,c.maxright,c.lr)}    }}FINDMAXIMUMSUBARRAY(A: A, low: 0, high: A.count-1)

0 0