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Commit 8f5c4b9

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150 solved. (#48)
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‎README.md

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* [9. Palindrome Number](src/0009_palindrome_number/palindrome_number.go)
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* [13. Roman to Integer](src/0013_roman_to_integer/roman_to_integer.go)   *`string`*
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* [66. Plus One](src/0066_plus_one/plus_one.go)   *`array`*
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* [150. Evaluate Reverse Polish Notation](src/0150_evaluate_reverse_polish_notation/evaluate_reverse_polish_notation.go)   *`stack`*
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<details>
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</details>
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/*
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150. Evaluate Reverse Polish Notation
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https://leetcode.com/problems/evaluate-reverse-polish-notation/
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Evaluate the value of an arithmetic expression in Reverse Polish Notation.
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Valid operators are +, -, *, /. Each operand may be an integer or another expression.
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Note:
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Division between two integers should truncate toward zero.
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The given RPN expression is always valid.
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That means the expression would always evaluate to a result and there won't be any divide by zero operation.
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*/
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// time: 2019年01月07日
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package evaluatereversepolishnotation
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import "strconv"
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// stack
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// time complexity: O(n)
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// space complexity: O(n)
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func evalRPN(tokens []string) int {
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stack := make([]int, len(tokens))
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top := -1
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for i := 0; i < len(tokens); i++ {
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switch ch := tokens[i]; ch {
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case "+":
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stack[top-1] += stack[top]
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top--
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case "-":
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stack[top-1] -= stack[top]
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top--
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case "*":
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stack[top-1] *= stack[top]
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top--
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case "/":
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stack[top-1] /= stack[top]
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top--
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default:
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top++
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stack[top], _ = strconv.Atoi(ch)
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}
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}
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return stack[0]
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}
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package evaluatereversepolishnotation
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import "testing"
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func TestEvalRPN(t *testing.T) {
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testCases := [][]string{
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{"2", "1", "+", "3", "*"},
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{"4", "13", "5", "/", "+"},
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{"10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"},
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{"4", "3", "-"},
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}
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expected := []int{9, 6, 22, 1}
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for index, tokens := range testCases {
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if res := evalRPN(tokens); res != expected[index] {
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t.Errorf("expected %d, got %d", expected[index], res)
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}
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}
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}

‎src/README.md

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|0122|[122. Best Time to Buy and Sell Stock II](0122_best_time_to_buy_and_sell_stock_2/maxprofit.go)|Easy|*`greedy`*|
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|0125|[Valid Palindrome](0125_valid_palindrome/valid_palindrome.go)|Easy||
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|0144|[144. Binary Tree Preorder Traversal](0144_binary_tree_preorder_traversal/binary_tree_preorder_traversal.go)|Medium|*`binary tree`*|
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|0150|[150. Evaluate Reverse Polish Notation](0150_evaluate_reverse_polish_notation/evaluate_reverse_polish_notation.go)|Medium|*`stack`*|
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|0167|[Two Sum II - Input array is sorted](./0167_two_sum2/two_sum2.go)|Easy|*`对撞指针(双索引)`*|
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|0198|[House Robber](./0198_house_robber/house_robber.go)|Easy|*`memory search;`* *`dynamic programming`*|
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|0209|[Minimum Size Subarray Sum](./0209_minimum_size_subarray_sum/minimum_size_subarray_sum.go)|Medium|*`sliding window`*|

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