Leetcode 36-40 Questions of solving code

Valid Sudoku

Determine if a Sudoku is valid, according To:sudoku puzzles-the Rules.

The Sudoku board could be partially filled, where empty cells is filled with the character ‘.‘ .

A partially filled sudoku which is valid.

Determine if the current state of Sudoku is legal

Class Solution {public:    bool Isvalidsudoku (vector<vector<char>>& board)     {        int col[10][ 10],ROW[10][10],BOX[10][10];        int i,j,x,a;        memset (col,0,sizeof (col));        memset (row,0,sizeof (Row));        memset (box,0,sizeof (box));        for (i=0;i<9;i++) for            (j=0;j<9;j++)                if (board[i][j]!= '. ')                {                    x=board[i][j]-' 0 ';                    A=I/3*3+J/3;                    if (row[i][x]==1 | | col[j][x]==1 | | box[a][x]==1) return false;                    else row[i][x]=col[j][x]=box[a][x]=1;                }                        return true;    }};

Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.

Empty cells is indicated by the character ‘.‘ .

Assume that there would be is only one unique solution.

A Sudoku Puzzle ...

... and its solution numbers marked in red.

DFS coefficient alone, guaranteeing the unique solution

Class Solution{int col[10][10],row[10][10],box[10][10];p ublic:void solvesudoku (vector<vector<char> >        & board) {memset (col,0,sizeof (col));        memset (row,0,sizeof (row));        memset (box,0,sizeof (box));            for (int i=0;i<9;i++) for (int j=0;j<9;j++) if (board[i][j]!= '. ')                {col[j][board[i][j]-' 0 ']=1;                row[i][board[i][j]-' 0 ']=1;            box[i/3*3+j/3][board[i][j]-' 0 ']=1;    } dfs (board,0);        } bool Dfs (vector<vector<char> > & board,int key) {int i,j;        if (key==81) return true;        int X=KEY/9;        int y=key%9;            if (board[x][y]!= '. ')        Return Dfs (BOARD,KEY+1);            else {int A=X/3*3+Y/3;                for (int i=1;i<=9;i++) if (col[y][i]==0 && row[x][i]==0 && box[a][i]==0) {                Col[y][i]=row[x][i]=box[a][i]=1; board[x][y]=i+ ' 0 ';                if (Dfs (board,key+1)) return true;                col[y][i]=row[x][i]=box[a][i]=0;            Board[x][y]= '. ';    }} return false; }};

Count and Say 

The Count-and-say sequence is the sequence of integers beginning as follows:
1, 11, 21, 1211, 111221, ...

1is read off as"one 1"Or11.
11is read off as"two 1s"Or21.
21is read off as"one 2, thenone 1"Or1211.

Given an integer n, generate the nth sequence.

Note:the sequence of integers would be represented as a string.

Simulation process

Class Solution {public:    string Countandsay (int n)    {        vector<int>mark[n+1];        int temp;        char ch;        Mark[1].push_back (1);        string ans;        int i,sum,j;        for (i=2;i<=n;i++)        {            temp=mark[i-1][0];            Sum=1;            For (J=1;j<mark[i-1].size (); j + +)            if (mark[i-1][j]!=temp)            {                mark[i].push_back (sum);                Mark[i].push_back (temp);                TEMP=MARK[I-1][J];                sum=1;            }            else    sum++;            Mark[i].push_back (sum);            Mark[i].push_back (temp);        }        Ans= "";        For (I=0;i<mark[n].size (); i++)        {            ch=mark[n][i]+ ' 0 ';            ans=ans+ch;        }        return ans;    };

Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C Where the candidate numbers sums to T.

The same repeated number is chosen from C unlimited number of times.

Note:

• All numbers (including target) would be positive integers.
• elements in a combination (a 1 ,  a 2 , ...,  a k ) must is in non-descending order. (Ie, a 1  ≤ a 2  ≤ ... ≤ a k ).
• The solution set must not contain duplicate combinations.

For example, given candidate set2,3,6,7and target7,
A Solution set is:
[7]
[2, 2, 3]

Types of output sequences and =target, reusable

Combination Sum II 

Given A collection of candidate numbers (C) and a target number (T), find all unique combinations in c where the candidate numbers sums to T.

Each number in C is used once in the combination.

Note:

• All numbers (including target) would be positive integers.
• elements in a combination (a 1 ,  a 2 , ...,  a k ) must is in non-descending order. (Ie, a 1  ≤ a 2  ≤ ... ≤ a k ).
• The solution set must not contain duplicate combinations.

For example, given candidate set10,1,2,7,6,1,5and target8,
A Solution set is:
[1, 7]
[1, 2, 5]
[2, 6]
[1, 1, 6]

Above, add a condition, the number of occurrences can only be used once

Class solution {vector<vector<int> >ans;vector<int>num;int key;int len;private:void dfs (vector< Int>mark,int n,int Sum,int used) {    if (Sum==key)    {        ans.push_back (mark);        return;    }    if (N==len) return;    if (Sum+num[n]>key) return;    DFS (mark,n+1,sum,0);    if (num[n]==num[n-1] && used==0) return;    Mark.push_back (Num[n]);    DFS (mark,n+1,sum+num[n],1);    Mark.pop_back ();} Public:vector<vector<int>> combinationSum2 (vector<int>& candidates, int target) {    len= Candidates.size ();    Num=candidates;    Sort (Num.begin (), Num.end ());    Key=target;        vector<int>mark;    DFS (mark,0,0,1);    return ans;};

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Leetcode 36-40 Questions of solving code