平衡点

/**
 *
 * 1.平衡点问题 平衡点：比如int[] numbers = {1,3,5,7,8,25,4,20};
 * 25前面的总和为24，25后面的总和也是24，25这个点就是平衡点；假如一个数组中的元素，其前面的部分等于后面的部分，那么这个点的位序就是平衡点
 * 要求：返回任何一个平衡点
 *
 * @author fangtengfei
 * @date 2010-5-15
 */
public class BalancePoint {

 public static void main(String[] args) {
  // 有平衡点，且平衡点是个数据
  int[] hasBalancePointValueNumbers = { 1, 2, 3, 4, 5, 6, 7, 8 };
  // 有平衡点，且平衡点是索引
  int[] hasBalancePointIndexNumbers = { 1, 3, 5, 7, 8, 4, 20 };
  // 无平衡点
  int[] noBalancePointNumbers = { 1, 3, 5, 7, 8, 4, 20, 12, 13 };
 }

 private static int queryBalancePoint(int[] noBalancePointNumbers) {
  int frontIndex = 0, backIndex = noBalancePointNumbers.length - 1;
  int temp = 0;
  // 判断前后索引不相等，那临时数减去前面的大于零则++，小于0则--
  while (frontIndex != backIndex) {
   if (temp - noBalancePointNumbers[frontIndex] >= 0) {
    temp -= noBalancePointNumbers[frontIndex];
    frontIndex++;
   } else {
    temp += noBalancePointNumbers[backIndex];
    backIndex--;
   }
  }
  // 当索引一样时，临时数等于0则返回当前数，<>0则返回当前索引。
  if (backIndex - frontIndex == 0) {
   if (temp == 0) {
    return noBalancePointNumbers[frontIndex];
   }
   if (temp - noBalancePointNumbers[frontIndex] == 0) {
    return frontIndex;
   }
  }
  return -1;
 }

}