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package Algorithms.lintcode.math;

import java.util.ArrayList;

public class MajorityNumber {

/**

* @param nums: a list of integers

* @return: find a majority number

*/

public int majorityNumber(ArrayList<Integer> nums) {

// write your code

if (nums == null || nums.size() == 0) {

// No majority number.

return -1;

}

int candidate = nums.get(0);

// The phase 1: Voting.

int cnt = 1;

for (int i = 1; i < nums.size(); i++) {

if (nums.get(i) == candidate) {

cnt++;

} else {

cnt--;

if (cnt == 0) {

candidate = nums.get(i);

cnt = 1;

}

}

}

// The phase 2: Examing.

cnt = 0;

for (int i = 0; i < nums.size(); i++) {

if (nums.get(i) == candidate) {

cnt++;

}

}

// No majory number.

if (cnt <= nums.size() / 2) {

return -1;

}

return candidate;

}

}