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  • [LeetCode] Spiral Matrix II

    The idea is just to generate the matrix in the spiral order. First the up-most row (u), then the right-most column (r), then the down-most row (d), and finally the left-most column (l). After generating a row or a column, update the corresponding variable to continue the generation.

    The code is as follows.

     1 class Solution {
     2 public:
     3     vector<vector<int> > generateMatrix(int n) { 
     4         vector<vector<int> > mat(n, vector<int>(n));
     5         int u = 0, d = n - 1, l = 0, r = n - 1, num = 1;
     6         while(true) {
     7             // up
     8             for(int col = l; col <= r; col++) mat[u][col] = num++;
     9             if(++u > d) break;
    10             // right
    11             for(int row = u; row <= d; row++) mat[row][r] = num++;
    12             if(--r < l) break;
    13             // down
    14             for(int col = r; col >= l; col--) mat[d][col] = num++;
    15             if(--d < u) break;
    16             // left
    17             for(int row = d; row >= u; row--) mat[row][l] = num++;
    18             if(++l > r) break;
    19         }
    20         return mat;
    21     }
    22 };
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  • 原文地址:https://www.cnblogs.com/jcliBlogger/p/4719936.html
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