Leetcode (ok)167 11 (思路) 35 74 （*） 162 33 34 153

35. Search Insert Position(再做只需要想如何取区间)

class Solution {
public:
    int searchInsert(vector<int>& nums, int target) {
        int left = 0, right = nums.size();
        while(left < right){
            int mid = left + (right-left)/2;
            if(nums[mid] == target) return mid;
            else if(nums[mid] > target) right = mid;
            else left = mid+1;
        }
 
        return right;
    }
};

最重要的还是如何取区间

当right = nums.size(), 表示为左闭右开，此时终止循环时，left = right

74. Search a 2D Matrix（只需要想到思路）

class Solution {
private:
    int get(vectorint>> matrix, int index){
        int m = matrix.size(), n = matrix[0].size();
        //纵坐标
        int i = index/n;
        //横坐标
        int j = index%n;
        return matrix[i][j];
    }
public:
    bool searchMatrix(vectorint>>& matrix, int target) {
        int m = matrix.size(), n = matrix[0].size();//m是竖列，n是横列
        int left = 0, right = m*n-1;
        while(left <= right){
            int mid = left + (right-left)/2;
            if(get(matrix, mid) > target) right = mid-1;
            else if(get(matrix, mid) < target) left = mid+1;
            else return true;
        }
        return false;
 
    }
};

把二维的转换成一维的

162. Find Peak Element(*)

class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        int left = 0, right = nums.size()-1;
        while(left < right){
            int mid = left + (right-left)/2;
            if(nums[mid] > nums[mid+1]){
                right = mid;
            }else{
                left = mid+1;
            }
        }
        return right;
    }
};

33. Search in Rotated Sorted Array(*)

class Solution {
public:
    int search(vector<int>& nums, int target) {
        int left = 0, right = nums.size()-1;
        while(left <= right){
            int mid = left + (right-left)/2;
            if(nums[mid] == target) return mid;
            else if(nums[mid] >= nums[left]){
                //说明在断崖的左边，这里不要忘记等于
                if(target >= nums[left] && target < nums[mid]){
                    right = mid-1;
                }else{
                    left = mid+1;
                }
            }else{
                if(target > nums[mid] && target <= nums[right]){
                    left = mid+1;
                }else{
                    right = mid - 1;
                }
            }
        }
        return -1;
    }
};

先确定断崖和mid的关系， 在找有序的部分

34. Find First and Last Position of Element in Sorted Array(*)

class Solution {
private:
    int left_bound(vector<int>& nums, int target){
        int left = 0, right = nums.size()-1;
        while(left <= right){
            int mid = left + (right-left)/2;
            if(nums[mid] > target){
                right = mid-1;
            }else if(nums[mid] < target){
                left = mid+1;
            }else{
                right = mid -1;
            }
        }
        if(left >= nums.size()) return -1;
        return nums[left] == target ? left: -1;
    }
 
    int right_bound(vector<int>& nums, int target){
        int left = 0, right = nums.size()-1;
        while(left <= right){
            int mid = left + (right-left)/2;
            if(nums[mid] > target){
                right = mid-1;
            }else if(nums[mid] < target){
                left = mid+1;
            }else{
                left = mid +1;
            }
        }
        if(right < 0) return -1;
        return nums[right] == target ? right: -1;
    } 
public:
    vector<int> searchRange(vector<int>& nums, int target) {
        int lIndex = left_bound(nums, target);
        int rIndex = right_bound(nums, target);
        return {lIndex, rIndex};
    }
};

153. Find Minimum in Rotated Sorted Array

class Solution {
public:
    int findMin(vector<int>& nums) {
        if(nums.size() == 1) return nums[0];
        int left = 0, right = nums.size()-1;
        if(nums[left] < nums[right]) return nums[left];
        while(left <= right){
            int mid = left+(right-left)/2;
            if(nums[mid+1] < nums[mid]) return nums[mid+1];
            if(nums[mid-1] > nums[mid]) return nums[mid];
            if(nums[mid] > nums[0]){
                left = mid+1;
            }else{
                right = mid-1;
            }
        }
        return -1;
 
    }
};

167. Two Sum II - Input Array Is Sorted(OK)

lass Solution {
public:
    vector<int> twoSum(vector<int>& numbers, int target) {
        int left = 0, right = numbers.size()-1;
        while(left < right){
            int sum = numbers[left] + numbers[right];
            if(sum > target) right--;
            else if(sum < target) left++;
            else return {left+1, right+1};
        }
        return {-1, -1};
    }
};

11. Container With Most Water(ok)

class Solution {
public:
    int maxArea(vector<int>& height) {
        int res = 0;
        int left = 0, right = height.size()-1;
        while(left < right){
            int cur_area = min(height[left], height[right]) * (right-left);
            res = max(res, cur_area);
            if(height[left] < height[right]) left++;
            else right--;
        }
        return res;
    }
};