剑指offer编程题java实现

面试题三：查找二维数组中元素问题

public static void main(String[] args){
         int[][] num = {{1,2,8,9},{2,4,9,12},{4,7,10,13},{6,8,11,15}};
        search(num,7);
        
     }
      public static void search(int[][] arr,int target){
          int rows = arr.length;
          int columns = arr[0].length;
          int row = 0;
          int column = columns-1;
          
          while(row<=rows&&column>=0){
          if(target==arr[row][column]){
              System.out.println(target+"在第"+row+"行，第"+column+"列");
              break;
            }
          if(target>arr[row][column]){
              row++;
          }
          if(target<arr[row][column]){
              column--;
          }
         }
      }

面试题四：替换字符串中的空格

 public static void main(String[] args){
         int[][] num = {{1,2,8,9},{2,4,9,12},{4,7,10,13},{6,8,11,15}};
          String str = "we are happy";
          replaceBlank(str);

     }
     public static void replaceBlank(String str){

         char[] charOld = str.toCharArray();
         char[] charNew = new char[100];
         for(int j = 0;j<charOld.length;j++){
             charNew[j] = charOld[j];
         }
         int blank = 0;
          for(int i = 0;i<charNew.length;i++){
              if(charNew[i]==‘ ‘){
                  blank++;
              }
          }
          int lengthFront = charOld.length-1;

          int lengthBack = charOld.length+2*blank-1;

          while(lengthFront>=0&&lengthBack>=0){
              if(charNew[lengthFront]!=‘ ‘){
                  charNew[lengthBack--] = charNew[lengthFront];
              }
              else
              {
                  charNew[lengthBack--] = ‘0‘;
                  charNew[lengthBack--] = ‘2‘;
                  charNew[lengthBack--] = ‘%‘;
                  lengthFront--;
              }
              lengthFront--;
          }
          System.out.println(charNew);

     }