USACO Training 1.5 Number Triangles

Consider the number triangle shown below. Write a program that calculates the highest sum of numbers that can be passed on a route that starts at the top and ends somewhere on the base. Each step can go either diagonally down to the left or diagonally down to the right.

          7

        3   8

      8   1   0

    2   7   4   4

  4   5   2   6   5

In the sample above, the route from 7 to 3 to 8 to 7 to 5 produces the highest sum: 30.

PROGRAM NAME: numtri

INPUT FORMAT

The first line contains R (1 <= R <= 1000), the number of rows. Each subsequent line contains the integers for that particular row of the triangle. All the supplied integers are non-negative and no larger than 100.

SAMPLE INPUT (file numtri.in)

5
7
3 8
8 1 0
2 7 4 4
4 5 2 6 5

OUTPUT FORMAT

A single line containing the largest sum using the traversal specified.

SAMPLE OUTPUT (file numtri.out)

30

题目的大致意思就是让你在这个number triangle往斜方，正下方，找最大的树，问最大的这些数的和是多少。

usaco还有一个奇怪的规则，输出完必须加endl。。。要不然过不了！

/*
ID: choiyin1
LANG: C++
TASK: numtri
*/
 
#include  
using namespace std;
 
int n,ans;
int main() {
    freopen("numtri.in", "r", stdin);
    freopen("numtri.out", "w", stdout);
    cin >> n;
    int numMax[1050];
    int num[1050];
    for (int i = 1; i <= n; i ++){
        for (int j = 1; j < i + 1; j ++) 
            cin>>num[j]; 
        for (int j = i; j > 0; j --)
            numMax[j] = max(numMax[j - 1], numMax[j]) + num[j];
    } 
    for (int i = 1; i<= n; i ++){
        ans = max(ans, numMax[i]);
    }
    cout << ans<
}