SpiralMatrix2-59

problem

Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

Example:

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>Input: 3
>Output:
>[
> [ 1, 2, 3 ],
> [ 8, 9, 4 ],
> [ 7, 6, 5 ]
>]
>

key

虽然标了medium,但是确实很简单,形成一个口字型闭环,一层层去处理就好了,然后再主要就是控制口字循环时候的边界,以及最后一个元素的判断

solution

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public int[][] generateMatrix(int n) {
int [][]res = new int[n][n];
int left = 0;
int right = n-1;
int top = 0;
int bottom = n-1;
int index = 1;
int quit = n*n;
while(index<=quit){
for(int i=left;i<=right;i++) {
res[top][i] = (index++);
}
top++;
for(int i=top;i<=bottom;i++){
res[i][right] = (index++);
}
right--;
for(int i=right;i>=left;i--) {
res[bottom][i]=(index++);
}
bottom--;
for(int i=bottom;i>=top;i--) {
res[i][left]=(index++);
}
left++;
}
return res;
}

perfect

no