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# 剑指 Offer 03. 数组中重复的数字

1690789584028

int main() {
    map<int, int> mp;
    cout << mp[1] << endl; // 输出 0，同时将 & lt;1,0 > 插入了
    if(mp.find(1) == mp.end()) {
        cout << "not find" << endl;
    }else{
        cout << "find" << endl;  // 输出这个
    }
    if(mp.find(2) == mp.end()) {
        cout << "not find" << endl;  // 输出这个
    }else{
        cout << "find" << endl;
    }
    return 0;
}
class Solution {
public:
    int findRepeatNumber(vector<int>& nums) {
        map<int, int> mp;
        mp.find(2);
        mp.end()
        for(int num: nums){
            if(mp[num] == 0){
                mp[num] = 1;
            }else{
                return num;
            }
        }
    }
};
1690790105241
1690790369457
class Solution {
public:
    int findRepeatNumber(vector<int>& nums) {
        int i = 0;
        while(i < nums.size()) {
            if(nums[i] == i) {
                i++;
                continue;
            }
            if(nums[nums[i]] == nums[i])
                return nums[i];
            swap(nums[i],nums[nums[i]]);
        }
        return -1;
    }
};
# 剑指 Offer 04. 二维数组中的查找
1690791767815
class Solution {
public:
    bool findNumberIn2DArray(vector<vector<int>>& matrix, int target) {
        
        if(matrix.size()==0 || matrix[0].size() == 0){
            return false;
        }
        
        int i_length = matrix.size(), j_length = matrix[0].size();
        int i = 0, j = j_length - 1;
        bool res = false;
        while(i < i_length && j >= 0){
            int cur = matrix[i][j];
            if(cur == target) {
                res = true;
                break;
            }else if(cur > target){
                j--;
            }else if(cur < target){
                i++;
            }
        }
        return res;
    }
};
# 剑指 Offer 50. 第一个只出现一次的字符
unordered_map 并不是按照插入的顺序排序的
1690793702147
class Solution {
public:
    char firstUniqChar(string s) {
        map<char, int> mp;
        
        for(char ch: s){
            if(mp[ch] == 0){
                mp[ch] = 1;
            }else{
                mp[ch] += 1;
            }
        }
        
        char res = ' ';
        for(char ch: s){
            if(mp[ch] == 1){
                res = ch;
                break;
            }
        }
        return res;
    }
};