|
| 1 | +////////////////////////////////////////////////////////////////////////////// |
| 2 | +// Depth First Search (DFS) |
| 3 | +// Time: O(m*n) |
| 4 | +// Space: O(m*n) |
| 5 | +// You can implement either Depth First Search (DFS) or Breadth First Search |
| 6 | +// (BFS). The only noticeable impact is the performance cost of the BFS queue |
| 7 | +// is higher than the DFS call stack. Also note if you are implementing BFS |
| 8 | +// that you should terminate the search at the dequeue call if the coordinates |
| 9 | +// signify that the cell has already been traversed as well as terminating the |
| 10 | +// search before the enqueue call at each of the four supplemental directions. |
| 11 | +////////////////////////////////////////////////////////////////////////////// |
| 12 | + |
| 13 | +classDrains{ |
| 14 | +constructor(west=false,east=false){ |
| 15 | +this.west=west; |
| 16 | +this.east=east; |
| 17 | +} |
| 18 | +} |
| 19 | + |
| 20 | +/** |
| 21 | + *@param {number[][]} heights |
| 22 | + *@return {number[][]} |
| 23 | + */ |
| 24 | +functionpacificAtlantic(heights){ |
| 25 | + |
| 26 | +constrowLen=heights.length; |
| 27 | +constcolLen=heights[0].length; |
| 28 | +constlastRow=rowLen-1; |
| 29 | +constlastCol=colLen-1; |
| 30 | +constdrainage=newArray(rowLen); |
| 31 | +constdrainsBoth=[]; |
| 32 | + |
| 33 | +for(letr=0;r<rowLen;++r){ |
| 34 | +drainage[r]=newArray(colLen); |
| 35 | +for(letc=0;c<colLen;++c){ |
| 36 | +drainage[r][c]=newDrains(); |
| 37 | +} |
| 38 | +} |
| 39 | + |
| 40 | +for(letr=0;r<rowLen;++r){ |
| 41 | +markDrainage(r,0,true); |
| 42 | +markDrainage(r,lastCol); |
| 43 | +} |
| 44 | +for(letc=0;c<colLen;++c){ |
| 45 | +markDrainage(0,c,true); |
| 46 | +markDrainage(lastRow,c); |
| 47 | +} |
| 48 | + |
| 49 | +returndrainsBoth; |
| 50 | + |
| 51 | +/** |
| 52 | + *@param {number} r |
| 53 | + *@param {number} c |
| 54 | + *@param {boolean=} west = `false` |
| 55 | + *@param {number=} prev = `-Infinity` |
| 56 | + *@return {void} |
| 57 | + */ |
| 58 | +functionmarkDrainage(r,c,west=false,prev=-Infinity){ |
| 59 | + |
| 60 | +if(!inBounds(r,c) |
| 61 | +||heights[r][c]<prev |
| 62 | +||(west&&drainage[r][c].west) |
| 63 | +||(!west&&drainage[r][c].east) |
| 64 | +){ |
| 65 | +return; |
| 66 | +} |
| 67 | + |
| 68 | +constdrains=drainage[r][c]; |
| 69 | +constheight=heights[r][c]; |
| 70 | + |
| 71 | +if(west){ |
| 72 | +drains.west=true; |
| 73 | +}else{ |
| 74 | +drains.east=true; |
| 75 | +} |
| 76 | + |
| 77 | +if(drains.west&&drains.east){ |
| 78 | +drainsBoth.push([r,c]); |
| 79 | +} |
| 80 | + |
| 81 | +markDrainage(r-1,c,west,height); |
| 82 | +markDrainage(r+1,c,west,height); |
| 83 | +markDrainage(r,c-1,west,height); |
| 84 | +markDrainage(r,c+1,west,height); |
| 85 | +} |
| 86 | + |
| 87 | +/** |
| 88 | + *@param {number} r |
| 89 | + *@param {number} c |
| 90 | + *@return {boolean} |
| 91 | + */ |
| 92 | +functioninBounds(r,c){ |
| 93 | +returnr>=0&&c>=0&&r<rowLen&&c<colLen; |
| 94 | +} |
| 95 | +} |