zoukankan      html  css  js  c++  java
  • LeetCode Weekly Contest 8

    LeetCode Weekly Contest 8

    415. Add Strings

    • User Accepted: 765
    • User Tried: 822
    • Total Accepted: 789
    • Total Submissions: 1844
    • Difficulty: Easy

    Given two non-negative numbers num1 and num2 represented as string, return the sum of num1 and num2.

    Note:

    1. The length of both num1 and num2 is < 5100.
    2. Both num1 and num2 contains only digits 0-9.
    3. Both num1 and num2 does not contain any leading zero.
    4. You must not use any built-in BigInteger library or convert the inputs to integer directly.

     简单的模拟题。

    class Solution {
    public:
        string addStrings(string num1, string num2) {
            int len1 = num1.length(), len2 = num2.length(); 
            int t = 0, c = 0, i = len1-1, j = len2-1; 
            string ret = ""; 
            while(i>=0 && j>=0){
                c = (t + (num1[i]-'0') + (num2[j]-'0'))%10; 
                t = (t + (num1[i]-'0') + (num2[j]-'0'))/10; 
                ret.insert(ret.begin(), char('0' + c)); 
                --i; --j; 
            }
            while(i>=0){
                c = (t + (num1[i]-'0'))%10; 
                t = (t + (num1[i]-'0'))/10;
                ret.insert(ret.begin(), char('0' + c));
                --i; 
            }
            while(j>=0){
                c = (t +  (num2[j]-'0'))%10; 
                t = (t +  (num2[j]-'0'))/10; 
                ret.insert(ret.begin(), char('0' + c)); 
                --j; 
            }
            if(t != 0){
                ret.insert(ret.begin(), char('0' + t)); 
            }
            return ret; 
        }
    };
    

      

    416. Partition Equal Subset Sum

    • User Accepted: 488
    • User Tried: 670
    • Total Accepted: 506
    • Total Submissions: 1689
    • Difficulty: Medium

    Given a non-empty array containing only positive integers, find if the array can be partitioned into two subsets such that the sum of elements in both subsets is equal.

    Note:
    Both the array size and each of the array element will not exceed 100.

    Example 1:

    Input: [1, 5, 11, 5]

     

    Output: true

     

    Explanation: The array can be partitioned as [1, 5, 5] and [11].

    Example 2:

    Input: [1, 2, 3, 5]

     

    Output: false

     

    Explanation: The array cannot be partitioned into equal sum subsets.

    简单的单重背包问题

    class Solution {
    public:
        bool canPartition(vector<int>& nums) {
            int sum = 0, len = nums.size(); 
            for(int i=0; i<len; ++i){
                sum += nums[i]; 
            }
            if(sum%2 != 0){
                return false; 
            }
            int* dp = new int[sum/2 + 1]; 
            for(int i=sum/2; i>=1; --i){
                dp[i] = 0; 
            }
            dp[0] = 1;
            for(int i=0; i<len; ++i){
                for(int j=sum/2; j>=nums[i]; --j){
                    if(dp[j-nums[i]]){
                        dp[j] = 1; 
                    }
                }
            }
            bool flag = (dp[sum/2]==1); 
            delete[] dp; 
            return flag; 
        }
    };
    

      

    417. Pacific Atlantic Water Flow

    • User Accepted: 259
    • User Tried: 403
    • Total Accepted: 265
    • Total Submissions: 1217
    • Difficulty: Medium

    Given an m x n matrix of non-negative integers representing the height of each unit cell in a continent, the "Pacific ocean" touches the left and top edges of the matrix and the "Atlantic ocean" touches the right and bottom edges.

    Water can only flow in four directions (up, down, left, or right) from a cell to another one with height equal or lower.

    Find the list of grid coordinates where water can flow to both the Pacific and Atlantic ocean.

    Note:

    1. The order of returned grid coordinates does not matter.
    2. Both m and n are less than 150.

    Example:

    Given the following 5x5 matrix:

     

      Pacific ~   ~   ~   ~   ~

           ~  1   2   2   3  (5) *

           ~  3   2   3  (4) (4) *

           ~  2   4  (5)  3   1  *

           ~ (6) (7)  1   4   5  *

           ~ (5)  1   1   2   4  *

              *   *   *   *   * Atlantic

     

    Return:

     

    [[0, 4], [1, 3], [1, 4], [2, 2], [3, 0], [3, 1], [4, 0]] (positions with parentheses in above matrix).

    双重bfs, 要注意不能重复采集到顶点。

    class Solution {
    public:
        int dx[4] = {0, 0, -1, 1}; 
        int dy[4] = {-1, 1, 0, 0}; 
        vector<pair<int, int>> pacificAtlantic(vector<vector<int>>& matrix) {
            vector<pair<int,int>> ret; 
            int m = matrix.size(); 
            if(m == 0){ return ret; } 
            int n = matrix[0].size(); 
            if(n == 0){ return ret; } 
            
            vector<vector<int>> cnt(m, vector<int>(n, 0)); 
            vector<vector<int>> vis(m, vector<int>(n, 0)); 
            int tmp, cur_x, cur_y, tmp_x, tmp_y, i = 0, j = 0;
            queue<pair<int, int>> qt;
            for(int i=0; i<m; ++i){
                qt.push(make_pair(i, 0)); 
                cnt[i][0] += 1; 
                vis[i][0] = 1; 
            }
            for(int i=1; i<n; ++i){
                qt.push(make_pair(0, i));
                cnt[0][i] += 1;
                vis[0][i] = 1; 
            }
            while(!qt.empty()){
                cur_x = qt.front().first;  cur_y = qt.front().second; 
                tmp = matrix[cur_x][cur_y]; 
                qt.pop(); 
                for(int i=0; i<4; ++i){
                    tmp_x = cur_x + dx[i]; tmp_y = cur_y + dy[i]; 
                    if(tmp_x>=0 && tmp_x<m && tmp_y>=0 && tmp_y<n && !vis[tmp_x][tmp_y] && matrix[tmp_x][tmp_y]>=tmp){
                        qt.push(make_pair(tmp_x, tmp_y)); 
                        cnt[tmp_x][tmp_y] += 1;
                        vis[tmp_x][tmp_y] = 1; 
                    }
                }
            }
            for(int i=0; i<m; ++i){
                for(int j=0; j<n; ++j){
                    vis[i][j] = 0; 
                }
            }
            for(int i=0; i<m; ++i){
                qt.push(make_pair(i, n-1)); 
                cnt[i][n-1] += 1; 
                vis[i][n-1] = 1; 
            }
            for(int i=0; i<n-1; ++i){
                qt.push(make_pair(m-1, i));
                cnt[m-1][i] += 1;
                vis[m-1][i] = 1; 
            }
            while(!qt.empty()){
                cur_x = qt.front().first;  cur_y = qt.front().second; 
                tmp = matrix[cur_x][cur_y]; 
                qt.pop(); 
                for(int i=0; i<4; ++i){
                    tmp_x = cur_x + dx[i]; tmp_y = cur_y + dy[i]; 
                    if(tmp_x>=0 && tmp_x<m && tmp_y>=0 && tmp_y<n && !vis[tmp_x][tmp_y] && matrix[tmp_x][tmp_y]>=tmp){
                        qt.push(make_pair(tmp_x, tmp_y)); 
                        cnt[tmp_x][tmp_y] += 1;
                        vis[tmp_x][tmp_y] = 1; 
                    }
                }
            }        
            for(int i=0; i<m; ++i){
                for(int j=0; j<n; ++j){
                    if(cnt[i][j] == 2){
                        ret.push_back(make_pair(i, j)); 
                    }
                }
            }
            return ret; 
        }
    };
    

      

  • 相关阅读:
    Asp.Net Web API 2第一课——入门
    Servlet之ServletContext获取web上下文路径、全局参数、和Attribute(域)
    jsp 获取服务器ip 以及端口号
    对String值不可变的理解以及String类型的引用传递问题
    关于 SAXParseException Content is not allowed in Prolog (前言中不允许有内容)
    用tomcat插件 在Eclipse 中配置Tomcat项目
    docker保存日志文件到本地
    java split函数结尾空字符串被丢弃的问题
    byte类型的127+1=-128?
    java 中 Integer 传参方式的问题
  • 原文地址:https://www.cnblogs.com/zhang-yd/p/5943230.html
Copyright © 2011-2022 走看看