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+#!/usr/bin/env lua
+
+--[[
+Challenge 093
+
+TASK #2 > Sum Path
+Submitted by: Mohammad S Anwar
+You are given binary tree containing numbers 0-9 only.
+
+Write a script to sum all possible paths from root to leaf.
+
+Example 1:
+Input:
+     1
+    /
+   2
+  / \
+ 3   4
+
+Output: 13
+as sum two paths (1->2->3) and (1->2->4)
+Example 2:
+Input:
+     1
+    / \
+   2   3
+  /   / \
+ 4   5   6
+
+Output: 26
+as sum three paths (1->2->4), (1->3->5) and (1->3->6)
+--]]
+
+
+-- read standard input into array
+function read_input()
+    local lines = {}
+    while true do
+        local line = io.read()
+        if line == nil then break end
+        lines[#lines + 1] = line
+    end
+    return lines
+end
+
+-- get a character from lines, blank if out of bounds
+function ch(lines, row, col)
+    if row<1 or row>#lines then return ' ' end
+    if col<1 or col>#(lines[row]) then return ' ' end
+    return string.sub(lines[row], col, col)
+end
+
+-- parse a subtree at row,col
+function parse_subtree(lines, row, col)
+    local tree = {}
+    tree.value = tonumber(ch(lines,row,col))
+    
+    if ch(lines, row + 1, col - 1) == '/' then
+        tree.left = parse_subtree(lines, row + 2, col - 2)
+    end
+    
+    if ch(lines, row + 1, col + 1) == '\\' then
+        tree.right = parse_subtree(lines, row + 2, col + 2)
+    end
+    
+    return tree
+end
+
+-- parse a tree, return root Node
+function parse_tree(lines)
+    local col = string.find(lines[1], "%d")
+    return parse_subtree(lines, 1, col)
+end
+
+-- return the subtree path len
+function add_subtree_paths(node, cur_len, total_len)
+    cur_len = cur_len + node.value
+    if node.left then 
+        total_len = add_subtree_paths(node.left, cur_len, total_len)
+    end
+    if node.right then
+        total_len = add_subtree_paths(node.right, cur_len, total_len)
+    end
+    if not node.left and not node.right then
+        total_len = total_len + cur_len
+    end
+    
+    return total_len
+end
+
+-- sum all sub-tree paths
+function add_tree_paths(tree)
+    return add_subtree_paths(tree, 0, 0)
+end
+
+io.write(add_tree_paths(parse_tree(read_input())), "\n")