平衡點

/**
 *
 * 1.平衡點問題 平衡點：比如int[] numbers = {1,3,5,7,8,25,4,20};
 * 25前面的總和爲24，25後面的總和也是24，25這個點就是平衡點；假如一個數組中的元素，其前面的部分等於後面的部分，那麼這個點的位序就是平衡點
 * 要求：返回任何一個平衡點
 *
 * @author fangtengfei
 * @date 2010-5-15
 */
public class BalancePoint {

 public static void main(String[] args) {
  // 有平衡點，且平衡點是個數據
  int[] hasBalancePointValueNumbers = { 1, 2, 3, 4, 5, 6, 7, 8 };
  // 有平衡點，且平衡點是索引
  int[] hasBalancePointIndexNumbers = { 1, 3, 5, 7, 8, 4, 20 };
  // 無平衡點
  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;
  // 判斷前後索引不相等，那臨時數減去前面的大於零則++，小於0則--
  while (frontIndex != backIndex) {
   if (temp - noBalancePointNumbers[frontIndex] >= 0) {
    temp -= noBalancePointNumbers[frontIndex];
    frontIndex++;
   } else {
    temp += noBalancePointNumbers[backIndex];
    backIndex--;
   }
  }
  // 當索引一樣時，臨時數等於0則返回當前數，<>0則返回當前索引。
  if (backIndex - frontIndex == 0) {
   if (temp == 0) {
    return noBalancePointNumbers[frontIndex];
   }
   if (temp - noBalancePointNumbers[frontIndex] == 0) {
    return frontIndex;
   }
  }
  return -1;
 }

}