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dc41a3c
Create 473.Matchsticks-to-Square_v2.cpp
Bill0412 60dd792
Create 2290.Minimum-Obstacle-Removal-to-Reach-Corner.cpp
wisdompeak 39070c7
Merge pull request #38 from Bill0412/patch-1
wisdompeak 2677ece
Update Readme.md
wisdompeak ce47ebc
Create Readme.md
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88 changes: 88 additions & 0 deletions
...inimum-Obstacle-Removal-to-Reach-Corner/2290.Minimum-Obstacle-Removal-to-Reach-Corner.cpp
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,88 @@ | ||
| class Solution { | ||
| vector<pair<int,int>>dir = {{1,0},{-1,0},{0,1},{0,-1}}; | ||
| public: | ||
| int minimumObstacles(vector<vector<int>>& grid) | ||
| { | ||
| int m = grid.size(); | ||
| int n = grid[0].size(); | ||
| if (m==1 && n==1) return 0; | ||
| vector<vector<int>>visited(m, vector<int>(n,0)); | ||
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| queue<pair<int,int>>q; | ||
| q.push({0,0}); | ||
| visited[0][0] = 1; | ||
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| int step = 0; | ||
| while (!q.empty()) | ||
| { | ||
| int len = q.size(); | ||
| while (len--) | ||
| { | ||
| auto [x, y] = q.front(); | ||
| q.pop(); | ||
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| for (auto [dx, dy]: dir) | ||
| { | ||
| int i = x+dx; | ||
| int j = y+dy; | ||
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| if (i<0||i>=m||j<0||j>=n) continue; | ||
| if (visited[i][j]==1) continue; | ||
| if (grid[i][j] == 1) | ||
| { | ||
| visited[i][j] = 1; | ||
| q.push({i,j}); | ||
| } | ||
| else | ||
| { | ||
| for (auto [ii, jj]: travel(grid, visited, i, j)) | ||
| { | ||
| if (ii==m-1 && jj==n-1) | ||
| return step; | ||
| q.push({ii,jj}); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| step++; | ||
| } | ||
| return 0; | ||
| } | ||
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| vector<pair<int,int>>travel(vector<vector<int>>& grid, vector<vector<int>>& visited, int x0, int y0) | ||
| { | ||
| int m = grid.size(); | ||
| int n = grid[0].size(); | ||
|
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| if (x0==m-1 && y0==n-1) | ||
| return {{x0, y0}}; | ||
|
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| queue<pair<int,int>>q; | ||
| q.push({x0,y0}); | ||
| visited[x0][y0] = 1; | ||
|
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| vector<pair<int,int>>rets; | ||
| while (!q.empty()) | ||
| { | ||
| auto [x, y] = q.front(); | ||
| q.pop(); | ||
|
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| for (auto [dx, dy] : dir) | ||
| { | ||
| int i = x+dx; | ||
| int j = y+dy; | ||
| if (i<0||i>=m||j<0||j>=n) continue; | ||
| if (visited[i][j]==1) continue; | ||
| visited[i][j] = 1; | ||
| if (i==m-1 && j==n-1) | ||
| rets.push_back({i,j}); | ||
| else if (grid[i][j]==1) | ||
| rets.push_back({i,j}); | ||
| else | ||
| q.push({i,j}); | ||
| } | ||
| } | ||
|
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| return rets; | ||
| } | ||
| }; |
5 changes: 5 additions & 0 deletions
BFS/2290.Minimum-Obstacle-Removal-to-Reach-Corner/Readme.md
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,5 @@ | ||
| ### 2290.Minimum-Obstacle-Removal-to-Reach-Corner | ||
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| 本题的本质就是从起点到终点,采用层级BFS,最少需要穿越几个回合的障碍。而障碍与障碍之间的空气,可以忽略不计。也就是说,某个障碍与空气相邻的话,下一个回合可以通过空气到达其他的障碍。 | ||
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| 在实现过程中,除了常规的层级BFS之外,我们还需要有一个travelAir的函数。travelAir以某个空格子为起点,遍历所有能"隔空"访问的障碍物。这些障碍物需要加入下一回合BFS的队列中去。 |
38 changes: 38 additions & 0 deletions
DFS/473.Matchsticks-to-Square/473.Matchsticks-to-Square_v2.cpp
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,38 @@ | ||
| class Solution { | ||
| bool divide2(vector<int>& sticks, int target) { | ||
| int n = sticks.size(); | ||
| for(int state = 0; state < (1<<n); ++state) { | ||
| int cur = 0; | ||
| for(int i = 0; i < n; ++i) { | ||
| if((state>>i)&1) cur += sticks[i]; | ||
| } | ||
| if(cur == target) return true; | ||
| } | ||
| return false; | ||
| } | ||
| public: | ||
| bool makesquare(vector<int>& matchsticks) { | ||
| int total = accumulate(matchsticks.begin(), matchsticks.end(), 0); | ||
| if(total % 4 != 0) return false; | ||
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| int n = matchsticks.size(); | ||
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| for(int state = 0; state < (1<<n); ++state) { | ||
| int cur = 0; | ||
| for(int i = 0; i < n; ++i) { | ||
| if((state>>i)&1) cur += matchsticks[i]; | ||
| } | ||
| if(cur == total / 2) { | ||
| vector<int> v1, v2; | ||
| for(int i = 0; i < n; ++i) { | ||
| if((state>>i)&1) v1.push_back(matchsticks[i]); | ||
| else v2.push_back(matchsticks[i]); | ||
| } | ||
|
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| if(divide2(v1, total / 4) && divide2(v2, total / 4)) return true; | ||
| } | ||
| } | ||
|
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| return false; | ||
| } | ||
| }; |
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