Created
November 10, 2014 03:41
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Spiral Matrix II
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| class Solution { | |
| public: | |
| void fill(vector<vector<int> > &vec, int dir, int idx, int start, int end, int &next) { | |
| switch(dir) { | |
| case 0: // left -> right | |
| for(int i = start; i <= end; i++) { | |
| vec[idx][i] = next; | |
| next++; | |
| } | |
| break; | |
| case 1: // up -> bottom | |
| for(int i = start; i <= end; i++) { | |
| vec[i][idx] = next; | |
| next++; | |
| } | |
| break; | |
| case 2: // right -> left | |
| for(int i = start; i >= end; i--) { | |
| vec[idx][i] = next; | |
| next++; | |
| } | |
| break; | |
| case 3: // bottom -> up | |
| for(int i = start; i >= end; i--) { | |
| vec[i][idx] = next; | |
| next++; | |
| } | |
| break; | |
| } | |
| } | |
| vector<vector<int> > generateMatrix(int n) { | |
| vector<vector<int> > vec; | |
| for(int i = 0; i < n; i++) { | |
| vector<int> r; | |
| for(int j = 0; j < n; j++) { | |
| r.push_back(0); | |
| } | |
| vec.push_back(r); | |
| } | |
| int gap = n, dir = 0, next = 1; | |
| int l = 0, r = n-1, u = 0, b = n-1; | |
| while(gap) { | |
| switch(dir) { | |
| case 0: | |
| fill(vec, dir, u, l, r, next); | |
| u++; | |
| gap = b - u + 1; | |
| dir = 1; | |
| break; | |
| case 1: | |
| fill(vec, dir, r, u, b, next); | |
| r--; | |
| gap = r - l + 1; | |
| dir = 2; | |
| break; | |
| case 2: | |
| fill(vec, dir, b, r, l, next); | |
| b--; | |
| gap = b - u + 1; | |
| dir = 3; | |
| break; | |
| case 3: | |
| fill(vec, dir, l, b, u, next); | |
| l++; | |
| gap = r - l + 1; | |
| dir = 0; | |
| break; | |
| } | |
| } | |
| return vec; | |
| } | |
| }; |
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