package com.xj.www.algo;
import java.util.Scanner;
/**
 * 分治演算法
 *
 * @author xiongjing
 *
 */
public class DivideTest {
      static int FalseCoin(int coin[], int low, int high) {
            int i, sum1, sum2, sum3;
            int re = 0;
            sum1 = sum2 = sum3 = 0;
            // 演算法具體實現
            // 判斷high == 1的情況
            if (low + 1 == high) {
                  if (coin[low] < coin[high]) {
                        re = low + 1;
                        return re;
                  } else {
                        re = high + 1;
                        return re;
                  }
            }
            // 判斷偶數的情況
            if ((high - low + 1) % 2 == 0) {
                  // 將總數分為兩路計算
                  for (i = low; i <= low + (high - low) / 2; i++) {
                        sum1 += coin[i];
                  }
                  for (i = low + (high - low) / 2 + 1; i <= high; i++) {
                        sum2 += coin[i];
                  }
                  if (sum1 > sum2) {
                        re = FalseCoin(coin, low + (high - low) / 2 + 1, high);
                        return re;
                  } else if (sum1 < sum2) {
                        re = FalseCoin(coin, low, low + (high - low) / 2);
                        return re;
                  } else {
                  }
            }
            // 判斷奇數的情況
            else {
                  for (i = low; i <= low + (high - low) / 2 - 1; i++) {
                        sum1 += coin[i];
                  }
                  for (i = low + (high - low) / 2 + 1; i <= high; i++) {
                        sum2 += coin[i];
                  }
                  sum3 = coin[low + (high - low) / 2];
                  if (sum1 > sum2) {
                        re = FalseCoin(coin, low + (high - low) / 2 + 1, high);
                        return re;
                  } else if (sum1 < sum2) {
                        re = FalseCoin(coin, low, low + (high - low) / 2 - 1);
                  } else {
                  }
                  if (sum1 + sum3 == sum2 + sum3) {
                        re = low + (high - low) / 2 + 1;
                        return re;
                  }
            }
            return re;
      }
      // 方法主入口
      public static void main(String[] args) {
            int i, n;
            int weizhi;
            System.out.println("分治演算法求解假幣問題！");
            System.out.print("請輸入硬幣總的個數：");
            @SuppressWarnings("resource")
            Scanner sc = new Scanner(System.in);
            n = sc.nextInt();
            System.out.print("請輸入硬幣的真假:");
            int[] coin = new int[n];
            for (i = 0; i < n; i++) {
                  coin[i] = sc.nextInt();
            }
            weizhi = FalseCoin(coin, 0, n - 1);
            System.out.println("在上述" + n + "個硬幣中，第" + weizhi + "個硬幣是假的！");
      }
}