遞迴方法：

#include <stdio.h>
#define maxn 100

int buf[maxn][maxn];
int n;
int d(int i, int j){
	int t1, t2;
	return i == n ? buf[i][j] : buf[i][j] + (((t1 = d(i+1, j)) > (t2 = d(i+1, j+1))) ? t1 : t2);
}

int main(){
       /*5
	9
	12 15
	10 6 8
	2 18 9 5
	19 7 10 4 16
        結果 59*/
	int i, j;
	scanf("%d", &n);
	for(i = 1; i <=n; ++i)
		for(j = 1; j <= i; ++j)
			scanf("%d", &buf[i][j]);
	printf("%d\n", d(1, 1));
	
	return 0;
}
 

#include <stdio.h>
#include <string.h>
#define maxn 100

int buf[maxn][maxn];
int d[maxn][maxn];
int n;
int dfunc(int i, int j){
	if(d[i][j] >= 0)  return d[i][j];
	return d[i][j] = buf[i][j] + (i == n ? 0  : dfunc(i+1, j) >  dfunc(i+1, j+1) ? dfunc(i+1, j) : dfunc(i+1, j+1));
}

int main(){
	int i, j;
	scanf("%d", &n);
	for(i = 1; i <= n; ++i)
	  for(j = 1; j <= i; ++j)
	  	scanf("%d", &buf[i][j]);
    memset(d, -1, sizeof(d));
	printf("%d\n", dfunc(1, 1));
	
	return 0;
}
 

#include <stdio.h>
#define maxn 200

int d[maxn][maxn];
int n;
void dfunc(){
	int i, j;
	for(i = n - 1; i >= 1; --i)
		for(j = 1; j <= i; ++j)
		   d[i][j] += d[i+1][j] > d[i+1][j+1] ? d[i+1][j]:d[i+1][j+1];
} 

int main(){
	int i, j; 
	scanf("%d", &n);
	for(i = 1; i <= n; ++i)
		for(j = 1; j <= i; ++j)
		  scanf("%d", &d[i][j]);
	dfunc();
	printf("%d\n", d[1][1]);
	
	return 0;
}