74. 搜索二维矩阵
自己做
解：二分查找
class Solution {
public:bool searchMatrix(vector<vector<int>>& matrix, int target) {int row = 0; //标记target所在行while(row < (int)matrix.size() && matrix[row][0] <= target) //找到target所在行的下一行row++;row--;if(row < 0) //连首行都不可能存在targetreturn false;//二分查找int begin = 0;int end = (int)matrix[0].size() - 1;while(begin <= end){int mid = (begin + end) / 2;if(matrix[row][mid] == target)return true;if(matrix[row][mid] > target) //偏大，往左边找end = mid - 1;if(matrix[row][mid] < target) //偏小，往右边找begin = mid + 1;}return false;}
};
75. 颜色分类
自己做
解：计数法
class Solution {
public:void sortColors(vector<int>& nums) {int a = 0;int b = 0;int c = 0;int i;//计数for(i = 0; i < (int)nums.size(); i++){if(nums[i] == 0)a++;if(nums[i] == 1)b++;if(nums[i] == 2)c++;} //赋值i = 0;while(a > 0){nums[i] = 0;a--;i++;}while(b > 0){nums[i] = 1;b--;i++;}while(c > 0){nums[i] = 2;c--;i++;} }
};
76. 最小覆盖子串
自己做
解：滑动窗口
class Solution {
public:string minWindow(string s, string t) {//字符串t的初始计数map<char, int> t_num;//插入键值for(int i = 0; i < (int)t.size(); i++)t_num.insert(make_pair(t[i], 0));//记录个数for(int i = 0; i < (int)t.size(); i++)t_num[t[i]]++;//最终确定的子串int begin = 0;int end = (int)s.size();//过程中的子串int left = 0;int right = 0;//起始跳过非子串部分while(right < (int)s.size() && t_num.find(s[left]) == t_num.end()){ //跳过非子串元素left++;right++;}while(right < (int)s.size()){if(t_num.find(s[right]) != t_num.end()){ //子串元素t_num[s[right]]--;//判断是否取得一个子串bool is = true;map<char, int>::iterator p = t_num.begin();for(int i = 0; i < (int)t_num.size(); i++){if(p->second > 0){ //还有缺少的元素is = false;break;}p++;}if(is){ //如果取得了一个子串//对该子串再压缩（有多余元素的情况下）while(t_num[s[left]] < 0){t_num[s[left]]++; //还原left++;while(left < (int)s.size() && t_num.find(s[left]) == t_num.end()) //跳过非子串元素left++;if(left == (int)s.size()) //越界返回break; }if(right - left < end - begin){ //更短的子串begin = left;end = right;}//确定下一个子串起始t_num[s[left]]++; //还原left++;while(left < (int)s.size() && t_num.find(s[left]) == t_num.end()) //跳过非子串元素left++;if(left == (int)s.size()) //越界返回break;}}right++;}if(end == (int)s.size()) //找不到一个子串return "";string res;for(int i = begin; i <= end; i++)res.push_back(s[i]);return res;}
};
