ädded Dynamic programming solution to minimum path sum

Author: ignacio-chiazzo

64 Minimum Path Sum.js

@@ -6,29 +6,29 @@
 //     if(grid === null || grid.length === 0 || grid[0].length === 0){
 //         return 0;
 //     }
-    
+
 //     var dp = [[]];
-    
+
 //     dp[0][0] = grid[0][0];
-    
+
 //     for(var i = 1; i < grid.length; i++){
 //         dp.push([]);
 //         dp[i][0] = grid[i][0] + dp[i - 1][0];
 //     }
-    
+
 //     for(var j = 1; j < grid[0].length; j++){
 //         dp[0][j] = grid[0][j] + dp[0][j - 1];
 //     }
-    
+
 //     for(i = 1; i < grid.length; i++){
 //         for(j = 1; j < grid[i].length; j++){
 //             var val1 = dp[i - 1][j];
 //             var val2 = dp[i][j - 1];
-            
+
 //             dp[i][j] = Math.min(val1, val2) + grid[i][j];
 //         }
 //     }
-    
+
 //     return dp[dp.length - 1][dp[0].length - 1];
 // }
 
@@ -42,32 +42,69 @@
 var minimumTotal = function(triangle) {
     var preResult = [];
     var rows = triangle.length;
-    
+
     if(rows > 0) {
         preResult.push(triangle[0][0]);
     } else {
         return null;
     }
-    
+
     for(var row = 1; row < rows; row++) {
         var curResult = [];
-        
+
         for(var col = 0; col < triangle[row].length; col++) {
             var val;
-            
+
             if(col === 0) {
                 val = preResult[col];
             } else if(col === (triangle[row].length - 1)) {
                 val = preResult[col-1];
             } else {
                 val = Math.min(preResult[col-1], preResult[col]);
             }
-        
+
             curResult[col] = triangle[row][col] + val;
         }
-        
+
         preResult = curResult;
     }
-    
+
     return Math.min.apply(null, preResult);
-};
+};
+
+
+//DP Solution
+var minPathSum = function(grid) {
+    if(grid.length === 0) {
+        return 0;
+    }
+    var m = grid.length;
+    var n = grid[0].length;
+    var paths = [];
+
+    // Initialize paths with 0
+    for(var i = 0; i < m; i++) {
+        var rowtemp = [];
+        for(var j = 0; j < n; j++) {
+            rowtemp.push(0);
+        }
+        paths.push(rowtemp);
+    }
+
+    //Initialize first row
+    paths[0][0] = grid[0][0];
+    for(var c = 1; c < n; c++) {
+        paths[0][c] = paths[0][c-1] + grid[0][c];
+    }
+    //Initialize first column
+    for(var r = 1; r < m; r++) {
+        paths[r][0] = paths[r - 1][0] + grid[r][0];
+    }
+    for(var row = 1; row < m; row++) {
+        for(var column = 1; column < n; column++){
+            var previous = Math.min(paths[row][column - 1], paths[row - 1][column]);
+            paths[row][column] = previous + grid[row][column];
+        }
+    }
+    return paths[m-1][n-1];
+};