codechef Sums in a Triangle题解

Let's consider a triangle of numbers in which a number appears in the first line, two numbers appear in the second line, three in the third line, etc. Develop a program which will compute the largest of the sums of numbers that appear on the paths starting from the top towards the base, so that:

• on each path the next number is located on the row below, more precisely either directly below or below and one place to the right;
• the number of rows is strictly positive, but less than 100
• all numbers are positive integers between O and 99.

  Input

  In the first line integer n - the number of test cases (equal to about 1000).
  Then n test cases follow. Each test case starts with the number of lines which is followed by their content.

  Output

  For each test case write the determined value in a separate line.

  Example

  Input:
  2
  3
  1
  2 1
  1 2 3
  4 
  1 
  1 2 
  4 1 2
  2 3 1 1 
  
  Output:
  5
  9

  
  

  使用动态规划法解决本题。

  和一题leetcode题一样，从底往上查找路径。

  
  

  #include 
      
       
  #include 
       
         #include 
        
          #include 
         
           #include 
          
            using namespace std; int triPath(vector
           
             > &tri) { if (tri.empty()) return 0; vector
            
              path(tri.back()); for (int i = (int)tri.size() - 2; i >= 0 ; i--)//unsigned做减法会溢出！！！ { for (int j = 0; j < (int)tri[i].size(); j++) { path[j] = max(path[j], path[j+1]) + tri[i][j]; } } return path.front(); } int SumsinATriangle() { int T, n; scanf("%d", &T); while (T--) { scanf("%d", &n); vector
             
               > tri; for (int i = 1; i <= n; i++) { vector
              
                tmp(i); for (int j = 0; j < i; j++) { scanf("%d", &tmp[j]); } tri.push_back(tmp); } printf("%d\n", triPath(tri)); } return 0; }