leetcode spiral matrix

最新推荐文章于 2019-07-07 11:13:21 发布

原创最新推荐文章于 2019-07-07 11:13:21 发布 · 421 阅读

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本文介绍了一种遍历二维矩阵元素的螺旋顺序算法，并通过示例代码详细解释了实现过程。

    public ArrayList<Integer> spiralOrder(int[][] matrix) {
        // 
    	ArrayList<Integer> result = new ArrayList<Integer>();
    	
    	if(matrix == null) return result;
    	if(matrix.length < 1) return result;
    	
    	
    	
    	int rowNum = matrix.length, colNum = matrix[0].length;
    	boolean[][] flags = new boolean[matrix.length][matrix[0].length];
        
    	int left = 0, right = matrix[0].length, up = 0, down = matrix.length;
    	
    	int direction = 1;  // 1 right, 2 down, 3 left, 4 up
    	int curRow = 0, curCol = 0;

    	boolean going = true;
    	
    	while(going) {
    		if(direction == 1) {
    			//store num
    			if(!flags[curRow][curCol]) {
    				result.add(matrix[curRow][curCol]);
    				flags[curRow][curCol] = true;
    			} 
    			//judge direction
    			if(curCol+1 == colNum || flags[curRow][curCol+1]) { //has to turn down
    				if(curRow + 1 == rowNum) {going = false; continue;}
    				if(flags[curRow+ 1][curCol]) {going = false; continue;}
    				else {
    					direction = 2; continue;
    				}
    			} else {
    				curCol++;
    				continue;
    			}
    			
    		} else if(direction == 2) {
    			//store num
    			if(!flags[curRow][curCol]) {
    				result.add(matrix[curRow][curCol]);
    				flags[curRow][curCol] = true;
    			} 
    			//judge direction
    			if(curRow + 1 == rowNum || flags[curRow+1][curCol]) { // has to turn
    				if(curCol == 0) { going = false; continue;}
    				if(flags[curRow][curCol - 1]) {going = false; continue;}
    				else {
    					direction = 3; continue;
    				}
    			} else {
    				curRow++;
    				continue;
    			}
    		} else if(direction == 3) {
    			//store num
    			if(!flags[curRow][curCol]) {
    				result.add(matrix[curRow][curCol]);
    				flags[curRow][curCol] = true;
    			} 
    			//judge direction
    			if(curCol == 0 || flags[curRow][curCol-1]) { //has to turn up
    				if(curRow == 0) {going = false; continue;}
    				if(flags[curRow - 1][curCol]) {going = false; continue;}
    				else {
    					direction = 4; continue;
    				}
    			} else {
    				curCol--; continue;
    			}
    		} else if(direction == 4) {
    			//store num
    			if(!flags[curRow][curCol]) {
    				result.add(matrix[curRow][curCol]);
    				flags[curRow][curCol] = true;
    			} 
    			//judge direction
    			if(curRow == 0 || flags[curRow - 1][curCol]) { //has to turn right
    				if(curCol == colNum) { going = false; continue;}
    				if(flags[curRow][curCol + 1]) {going = false; continue;}
    				else {
    					direction = 1; continue;
    				}
    			} else {
    				curRow--;continue;
    			}
    		
    		}
    	}
    	
    	return result;
    }