剑指offer：子数组的最大和

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题目：输入一个整形数组，数组里有整数也有负数，数组中一个或者多个整数组成一个子数组，求所有子数组和的最大值。

package com.interview;public class FindGreatestSubArray {private boolean valid = true;  //这是为了标记输入是否有效的变量private int greatestSubArray(int[] A) {if (A.length < 1) {valid = false;return 0;}int result = A[0], sum = 0;for (int i = 0; i < A.length; ++i) {if (A[i] < 0) {if (result < 0) { //这是为了防止全是负数的情况if (result < A[i])result = A[i];} elsesum = 0;} else {if (A[i] >= 0)sum += A[i];if (result < sum)result = sum;}}return result;}public static void main(String[] args) {// TODO Auto-generated method stubFindGreatestSubArray fbsa = new FindGreatestSubArray();// int[] A = new int[] { -2, -2, 3, 10, 1, -4, 7, 2, 4, -5 };//int[] A = new int[] { -5, -3, -1, -2, -8 };//int[] A=new int[]{1};int[] A=new int[]{-2, -2, 3, 1, -4, 7, -5};int result = fbsa.greatestSubArray(A);if (result == 0) {if (!fbsa.valid)System.out.println("invalid input!");}System.out.println(result);}}

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