分治法求最值

package test02;public class Test01 {    public static void main(String[] args) {        int[] a = { 3, 4,1, 3, 22, 11, 33, 90, 1,2,12,90, 89};        int max = getMax(a, 0, a.length - 1);        int min = getMin(a, 0, a.length - 1);        System.out.println("最大值: " + max);        System.out.println("最小值：" + min);    }    public static int getMax(int a[], int begin, int end) {        int temp1 = 0;        int temp2 = 0;        if (begin == end) {            return temp1 = temp2 = a[begin];        } else if (begin == end - 1) {            temp1 = a[begin];            temp2 = a[end];            return temp1 > temp2 ? temp1 : temp2;        } else {            int mid = (begin + end) / 2;            temp1 = getMax(a, begin, mid);            temp2 = getMax(a, mid+1, end);            return temp1 > temp2 ? temp1 : temp2;        }    }    public static int getMin(int[] a, int begin, int end) {        int temp1 = 0;        int temp2 = 0;        if (begin == end) {            return temp1 = temp2 = a[begin];        } else if (begin == end - 1) {            temp1 = a[begin];            temp2 = a[end];            return temp1 > temp2 ? temp2 : temp1;        } else {            int mid = (begin + end) / 2;            temp1 = getMin(a, 0, mid);            temp2 = getMin(a, mid+1, end);            return temp1 > temp2 ? temp2 : temp1;        }    }}

栈结构实现

package test02;import java.util.Stack;public class Test02 {    public static void main(String[] args) {        int[] a = { 1, 2, 3, 5,-1,-1, 32, 12, 12,100, 43, 46, 12, 11,56 };        int max = getMax(a);        int min=getMin(a);        System.out.println("最大值： " + max);        System.out.println("最小值： "+min);    }    public static int getMax(int[] a) {        int temp;        int max = a[0];        Stack<Integer> stack = new Stack<Integer>();        stack.push(0);//把起始点压入栈        stack.push(a.length - 1);//把结尾点压入栈        while (!stack.isEmpty()) {//当栈不为空            int high = stack.pop();//从栈中取出待分元素段的起始，终止位置            int low = stack.pop();            while (high - low > 1) {                int mid = (high + low) / 2;                stack.push(mid + 1);                stack.push(high);                high = mid;//取前半段，准备继续对分            }            if (high - low == 1) {                temp = (a[high] > a[low]) ? a[high] : a[low];            } else {                temp = a[high];            }            if (temp > max) {                max = temp;            }        }        return max;    }    public static int getMin(int[] a){        int temp;        int min=a[0];        Stack<Integer>stack=new Stack<Integer>();        stack.push(0);        stack.push(a.length-1);        while(!stack.isEmpty()){            int high=stack.pop();            int low=stack.pop();            while(high-low>1){                int mid=(low+high)/2;                stack.push(mid+1);                stack.push(high);                high=mid;            }            if(high-low==1){                temp=(a[high]>a[low]?a[low]:a[high]);            }else{                temp=a[low];            }            if(temp<min){                min=temp;            }        }        return min;     }}