poj 1163 The Triangle

Description

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

(Figure 1)

Figure 1 shows a number triangle. Write a program that calculates the highest sum of numbers 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.

Input

Your program is to read from standard input. The first line contains one integer N: the number of rows in the triangle. The following N lines describe the data of the triangle. The number of rows in the triangle is > 1 but <= 100. The numbers in the triangle, all integers, are between 0 and 99. 

Output

Your program is to write to standard output. The highest sum is written as an integer.

Sample Input

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

Sample Output

30

代码如下

#include <cstdio>
#include <cstdlib>
#include <cstring>

int tri[102][102];
int sum[102][102];
int dir[][4] = {{1,0},{1,1}};
int n;

void dfs(int x, int y) {
    for(int i = 0; i < 2; i++) {
        int tmpx = x + dir[i][0];
        int tmpy = y + dir[i][1];
        if(tmpx < n && tmpy >= 0 && tmpy <= tmpx) {
            if(sum[tmpx][tmpy] < sum[x][y] + tri[tmpx][tmpy]) {
                sum[tmpx][tmpy] = sum[x][y] + tri[tmpx][tmpy];
                dfs(tmpx, tmpy);
            }
        }
    }
}

int main(int argc, char const *argv[])
{
    //freopen("input.txt","r",stdin);
    while(scanf("%d",&n) != EOF) {
        for(int i = 0; i < n; i++) {
            for(int j = 0; j <= i; j++) {
                scanf("%d",&tri[i][j]);    
            }
        }
        memset(sum, 0, sizeof(sum));
        sum[0][0] = tri[0][0];
        dfs(0,0);
        int max = 0;
        for(int i = 0; i < n; i++) {
            if(max < sum[n-1][i]) {
                max = sum[n-1][i];
            }
        }
        printf("%d\n",max);
    }
    return 0;
}

 这个题和3176基本一致，但把数组扩大后在3176上跑却一直WA，不明白为甚吗

改成dp的代码如下

#include <cstdio>
#include <string>
#include <iostream>
using namespace std;

int n;
int bow[352][352] = {0};

int main(int argc, char const *argv[])
{
    //freopen("input.txt","r",stdin);
    scanf("%d",&n);
    for(int i = 0; i < n; i++) {
        for(int j = 0; j <= i; j++) {
            scanf("%d",&bow[i][j]);
        }
    } 
    for(int i = n-2; i >= 0; i--) {
        for(int j = 0; j <= i; j++) {
            bow[i][j] = bow[i][j] + max(bow[i+1][j], bow[i+1][j+1]);
        }
    }
    printf("%d\n",bow[0][0]);
    return 0;
}