[LeetCode][JavaScript]Triangle

標籤：

Triangle

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

For example, given the following triangle

[     [2],    [3,4],   [6,5,7],  [4,1,8,3]]

 

The minimum path sum from top to bottom is 11 (i.e., 2 + 3 + 5 + 1 = 11).

Note:
Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.

https://leetcode.com/problems/triangle/

 

 

 

 

 

動態規劃，找個規律。

每一層都基於上一層的最小和來推斷當前的最小和。

第一個點的min只能是上層的結果加上自己；最後一個點的min只能是上層的結果加上自己;中間的點就2個選擇，上層對應下標的點和(對應下標 - 1)的點。

 1 /** 2  * @param {number[][]} triangle 3  * @return {number} 4  */ 5 var minimumTotal = function(triangle) { 6     var passed = triangle[0]; 7     if(triangle.length === 1){ 8         return passed[0]; 9     }10     var min = Infinity;11     for(var i = 1; i < triangle.length; i++){12         var row = triangle[i];13         var currRow = [];14         for(var j = 0; j < row.length; j++){15             var tmp = null;16             if(j === 0){17                 tmp = row[0] + passed[0];18             }else if(j === row.length - 1){19                 tmp = row[j] + passed[j - 1];20             }else{21                 tmp = Math.min(row[j] + passed[j], row[j] + passed[j - 1]);22             }23             currRow.push(tmp);24             if(i === triangle.length - 1){25                 if(tmp < min){26                     min = tmp;27                 }28             }29         }30         passed = currRow;31     }32     return min;33 };

 

 

 

 

[LeetCode][JavaScript]Triangle