Week1-2016

lonsest-substring.java

public int lengthOfLongestSubstring(String s) {
      if(s==null || s.length()==0){
        return 0;
      }
 
    HashSet<Character> set = new HashSet<Character>();
 
    int max=0;
 
    int i=0;
    int start=0;
    while(i<s.length()){
        
        char c = s.charAt(i);
        
        if(!set.contains(c)){
            set.add(c);
        }
        else{
            max = Math.max(max, set.size());
 
            while(s.charAt(start)!=c && start<i){
                set.remove(s.charAt(start));
                start++;
            }
            start++;
        }
 
        i++;
    }
 
    max = Math.max(max, set.size());
 
    return max;  
    }

spiral-matrix.java

public int[][] generateMatrix(int n) {
    		if(n<=1){
    		    return new int [n][n];
    		}
	        int [] [] mat = new int [n][n];
	        int[]counter= {0};//so we can pass by reference
	        Solution solution = new Solution();
	        solution.moveRight(mat, 0, 0, n, counter);
	        return mat;
	    }
		
		
		public void moveRight(int[][] mat,int r, int c,int limit,int[] counter){
			int n= mat[0].length*mat[0].length;
			int moves =0;
			while(moves<limit){
				mat[r][c]=++counter[0];
				c++;moves++;
			}
			if(counter[0]==n){
				return;
			}
			moveDown(mat,r+1,c-1,limit-1,counter);
		}
		public void moveDown(int[][] mat,int r, int c,int limit, int[] counter){
			int n= mat[0].length*mat[0].length;
			int moves=0;
			while( moves<limit){
				mat[r][c]=++counter[0];
				r++;moves++;
			}
			if(counter[0]==n){
				return;
			}
			moveLeft(mat,r-1,c-1,limit,counter);

		}
		public void moveLeft(int[][] mat,int r, int c,int limit, int[] counter){
			int n= mat[0].length*mat[0].length;
			int moves=0;
			while(moves<limit){
				mat[r][c]=++counter[0];
				c--;moves++;
			}
			if(counter[0]==n){
				return;
			}
			moveUp(mat,r-1,c+1,limit-1,counter);
		}
		public void moveUp(int[][] mat,int r, int c,int limit, int[] counter){
			int n= mat[0].length*mat[0].length;
			int moves=0;
			while(moves<limit){
				mat[r][c]=++counter[0];
				r--;moves++;
			}
			if(counter[0]==n){
				return;
			}
			moveRight(mat,r+1,c+1,limit,counter);

		}

valid-palindrome.java

public boolean isPalindrome(String s) {
        s=s.replaceAll("[^A-Za-z0-9 ]", "");
        s=s.replaceAll(" ", "");
        s=s.toLowerCase();
        int length= s.length();
        boolean even;
        if (length%2==0){
          even=true;  
        }
        else{
            even=false;
        }
            //odd algorithm
            int mid= (int)Math.floor(length/2);//for 0-indexed array
            int even_shift=even?1:0;//shift the middle tracker if even number of characters
            for(int i=even?0:1 ;(mid-even_shift-i)>=0; i++){
                if(s.charAt(mid-even_shift-i) != s.charAt(mid+i) ){
                    return false;
                }
            }
            return true;
        }