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Commit39e8398

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200 Number of Islands Union Find solution (neetcode-gh#366)
1 parentf69bc1c commit39e8398

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‎java/200-Number-of-Islands.java‎

Lines changed: 76 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -29,4 +29,80 @@ public void dfs(char[][] grid, int i, int j) {
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dfs(grid,i -1,j);
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dfs(grid,i,j -1);
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}
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publicintnumIslandsUnionFind(char[][]grid) {
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intm =grid.length;
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intn =grid[0].length;
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UnionFinduf =newUnionFind(grid);
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int[][]dirs = {{1,0},{-1,0},{0,1},{0,-1}};
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for (inti =0;i <m;i++)
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for (intj =0;j <n;j++)
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if (grid[i][j] =='1') {
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for (int[]dir :dirs) {
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intx =dir[0] +i;
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inty =dir[1] +j;
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if (isSafe(grid,x,y)) {
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intid1 =i*n +j;
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intid2 =x*n +y;
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uf.union(id1,id2);
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}
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}
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}
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returnuf.count();
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}
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privatebooleanisSafe(char[][]grid,intx,inty) {
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intm =grid.length;
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intn =grid[0].length;
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returnx >=0 &&x <m &&y >=0 &&y <n &&grid[x][y] !='0';
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}
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classUnionFind {
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privateintcount;
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privateint[]parent,size;
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publicUnionFind(char[][]grid) {
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intm =grid.length,n =grid[0].length;
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parent =newint[m*n];
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for (inti =0;i <m;i++)
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for (intj =0;j <n;j++) {
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if (grid[i][j] =='1') {
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intid =i*n +j;
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parent[id] =id;
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count++;
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}
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}
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}
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publicintfind(intp) {
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while(p !=parent[p]) {
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parent[p] =parent[parent[p]];
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p =parent[p];
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}
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returnp;
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}
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publicbooleanunion(intp,intq) {
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introot1 =find(p);
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introot2 =find(q);
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if (root1 ==root2)
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returnfalse;
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parent[root1] =root2;
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count--;
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returntrue;
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}
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publicintcount() {
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returncount;
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}
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}
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}

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