Add unique paths solution

Author: sudheerj

src/java1/algorithms/dynamicProgramming/UniquePaths.java

@@ -0,0 +1,41 @@
+package java1.algorithms.dynamicProgramming;
+import java.util.*;
+
+public class UniquePaths {
+    //Dynamic programming:- TC:O(m*n) OC:O(m*n)
+    private static int uniquePaths1(int m, int n) {
+        int[][] dp = new int[m][n];
+
+        for(int i=0; i<m; i++) {
+            for(int j=0; j<n; j++) {
+                if(i== 0 || j == 0) {
+                    dp[i][j] = 1;
+                } else {
+                    dp[i][j] = dp[i-1][j] + dp[i][j-1];
+                }
+            }
+        }
+        return dp[m-1][n-1];
+    }
+    //Dynamic programming:- TC:O(m*n) OC:O(n)
+    private static int uniquePaths2(int m, int n) {
+        int[] row = new int[n];
+        Arrays.fill(row, 1);
+
+        for(int i=1; i<m; i++){
+            int[] newRow = new int[n];
+            newRow[0] = 1;
+            for(int j=1; j<n; j++) {
+                newRow[j] = row[j] + newRow[j-1];
+            }
+            row = newRow;
+        }
+        return row[n-1];
+    }
+
+    public static void main(String[] args) {
+         int m = 4, n = 5;
+         System.out.println(uniquePaths1(m, n));
+         System.out.println(uniquePaths2(m, n));
+    }
+}

src/javascript/algorithms/dynamicProgramming/uniquePaths.js

@@ -0,0 +1,34 @@
+//Dynamic programming:- TC:O(m*n) OC:O(m*n)
+function uniquePaths1(m, n) {
+    let dp = new Array(m).fill(0).map(x => new Array(n).fill(0));
+
+    for(let i=0; i<m; i++) {
+        for(let j=0; j<n; j++) {
+            if(i === 0 || j === 0) {
+                dp[i][j] = 1;
+            } else {
+                dp[i][j] = dp[i-1][j] + dp[i][j-1];
+            }
+        }
+    }
+    return dp[m-1][n-1];
+}
+
+//Dynamic programming:- TC:O(m*n) OC:O(n)
+function uniquePaths2(m, n) {
+    let row = new Array(n).fill(1);
+
+    for(let i=1; i<m; i++) {
+        let newRow = new Array(n).fill(0);
+        newRow[0] = 1;
+        for(let j=1; j<n; j++) {
+            newRow[j] = row[j] + newRow[j-1];
+        }
+        row = newRow;
+    }
+    return row[n-1];
+}
+
+let m = 4, n = 5;
+console.log(uniquePaths1(m, n));
+console.log(uniquePaths2(m, n));