all possible paths

Author: okmd

backtracking/lb-17-all-possible-paths.cpp

@@ -0,0 +1,88 @@
+#include<iostream>
+#include<vector>
+#include<limits.h>
+#include<queue>
+using namespace std;
+int dx[] = { 1,0 };
+int dy[] = { 0,1 };
+vector<vector<int>>paths;
+bool safe(vector<vector<int>>& mat, int i, int j) {
+    int n = mat.size();
+    int m = mat[0].size();
+    return (i < n and j < m and i >= 0 and j >= 0 and mat[i][j] != -1);
+}
+void findPaths(vector<vector<int>>& mat, int i, int j, vector<int>& path) {
+    if (i == mat.size() - 1 and j == mat[0].size() - 1) {
+        path.push_back(mat[i][j]);
+        paths.push_back(path);
+        path.pop_back();
+        return;
+    }
+    if (!safe(mat, i, j)) return;
+
+    int orig = mat[i][j];
+    path.push_back(orig);
+    mat[i][j] = -1;
+    for (int k = 0; k < 2; k++) {
+        int p = i + dx[k], q = j + dy[k];
+        findPaths(mat, p, q, path);
+    }
+    mat[i][j] = orig;
+    path.pop_back();
+
+}
+// using Queue
+class cell {
+public:
+    int i, j;
+    vector<int> path;
+    cell(vector<int> p, int x, int y) {
+        path=p;
+        i = x;
+        j = y;
+    }
+};
+
+void findPaths(vector<vector<int>>& mat) {
+    int n = mat.size();
+    int m = mat[0].size();
+    vector<vector<int>>ans;
+    queue<cell> q;
+    q.push({ {mat[0][0]}, 0,0 });
+    while(!q.empty()){
+        auto p = q.front();
+        q.pop();
+        if(p.i==n-1 and p.j==m-1){
+            paths.push_back(p.path);
+        }
+        for (int k = 0; k < 2; k++) {
+            int x = p.i + dx[k], y = p.j + dy[k];
+            if(safe(mat, x, y)){
+                vector<int>temp= p.path;
+                temp.push_back(mat[x][y]);
+                q.push({temp,x,y});
+                temp.pop_back();
+            }
+        }
+    }
+}
+int main() {
+    // input matrix with hurdles shown with number 0
+    vector<vector<int>> mat = {
+        {1,2,3},{4,5,6},{7,8,9}
+    };
+    // find longest path with source (0, 0) and
+    // destination (1, 7)
+    int i = 0, j = 0;
+    vector<int> path;
+    findPaths(mat, i, j, path);
+    findPaths(mat);
+
+    for (auto path : paths) {
+        for (auto val : path)
+            cout << val << " ";
+        cout << endl;
+    }
+    return 0;
+}
+// https://leetcode.com/playground/QDwD9r84