android-notes/blogs/Algorithm/剑指 Offer/数组相关.md

数组相关

04. 二维数组中的查找

class Solution {

    public boolean findNumberIn2DArray(int[][] matrix, int target) {
        if (matrix == null || matrix.length == 0) {
            return false;
        }
        int m = matrix.length, n = matrix[0].length;
        int row = 0, col = n - 1;
        while (row < m && col >= 0) {
            if (matrix[row][col] > target) {
                col--;
            } else if (matrix[row][col] < target) {
                row++;
            } else {
                return true;
            }
        }
        return false;
    }
}

11. 旋转数组的最小数字

class Solution {

    public int minArray(int[] numbers) {
        int i = 0, j = numbers.length - 1;
        while (i < j) {
            int m = (i + j) / 2;
            if (numbers[m] > numbers[j]) {
                i = m + 1;
            } else if (numbers[m] < numbers[j]) {
                j = m;
            } else {
                j--;
            }
        }
        return numbers[i];
    }
}

21. 调整数组顺序使奇数位于偶数前面

class Solution {

    public int[] exchange(int[] nums) {
        int i = 0, j = nums.length - 1;
        while (i < j) {
            if (nums[i] % 2 == 1 && nums[j] % 2 == 0) {
                i++;
                j--;
            } else if (nums[i] % 2 == 1 && nums[j] % 2 == 1) {
                i++;
            } else if (nums[i] % 2 == 0 && nums[j] % 2 == 1) {
                int temp = nums[i];
                nums[i++] = nums[j];
                nums[j--] = temp;
            } else {
                j--;
            }
        }
        return nums;
    }
}

class Solution {

    public int[] exchange(int[] nums) {
        int i = 0, j = nums.length - 1, temp;
        while (i < j) {
            while (i < j && (nums[i] & 1) == 1) {
                i++;
            }
            while (i < j && (nums[j] & 1) == 0) {
                j--;
            }
            temp = nums[i];
            nums[i] = nums[j];
            nums[j] = temp;
        }
        return nums;
    }
}

39. 数组中出现次数超过一半的数字

class Solution {

    public int majorityElement(int[] nums) {
        Arrays.sort(nums);
        return nums[nums.length / 2];
    }
}

class Solution {

    public int majorityElement(int[] nums) {
        int count = 0, result = 0;
        for (int num : nums) {
            if (count == 0) {
                result = num;
            }
            count += (result == num) ? 1 : -1;
        }
        return result;
    }
}