Leetcode_二分查找

leetcode_704原题链接

class Solution {
    public int search(int[] nums, int target) {
        int high = nums.length-1;
        int low = 0;
        int value = 0;
        while(high>=low) {
            value = (high+low)/2;
            if (nums[value]==target) {
                return value;
            }
            else if (nums[value]>target) {
                high = value-1;
            }
            else {
                low = value+1;
            }
        }
        return -1;
    }
}

leetcode_35原题链接

class Solution {
    public int searchInsert(int[] nums, int target) {
        if (nums.length==0) {
            return 0;
        }
        int l = 0;
        int r = nums.length-1;
        int mid;
        while (l<r) {
            mid = l+(r-l)/2;
            if (nums[mid]==target) {
                return mid;
            }
            else if (nums[mid]>target) {
                r = mid;
            }
            else {
                l = mid+1;
            }
        }
        if (nums[l]>target) {
            return l;
        }
        else if(nums[l]<target){
            return l+1;
        }
        else {
            return l;
        }
}
}

leetcode_162寻找峰值

class Solution {
    public int findPeakElement(int[] nums) {
        if (nums.length == 0) {
            return -1;
        }
        int l = 0;
        int right = nums.length-1;
        int mid ;
        while (l<right) {
            mid = l+(right-l)/2;
            if (nums[mid]>nums[mid+1]) {
                right = mid;
            }
            else {
                l = mid+1;
            }
        }
        return l ;
    }
}

leetcode_74搜索二维矩阵

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        int m = matrix.length;
        int n = matrix[0].length;
        int l = 0;
        int r = m*n-1;
        int mid;
        while (l<r) {
            mid = l+(r-l)/2;
            if (matrix[mid/n][mid%n]==target) {
                return true;
            }
            else if (matrix[mid/n][mid%n]>target) {
                r = mid;
            }
            else {
                l = mid+1;
            }
        }
        if (matrix[l/n][l%n]==target) {
            return true;
        }
        return false;
        }
}