石子归并---区间型动态规划

#include<stdio.h>
#include<algorithm>
using namespace std;
int a[105];
int sum[105];
int d[105][105];
const int INF = (1 << 30);
int main(){
	int n, i;
	scanf("%d", &n);
	for (i = 1; i <= n; i++){
		scanf("%d", &a[i]);
		sum[i] = sum[i - 1] + a[i];
	}
	int len, j, k;
	for (len = 1; len < n; len++){
		for (i = 1; i <= n - len; i++){
			int res = INF;
			j = i + len;
			for (k = i; k < j; k++)
				res = min(res, d[i][k] + d[k + 1][j] + sum[j] - sum[i - 1]);
			d[i][j] = res;
		}
	}
	printf("%d\n", d[1][n]);
	return 0;
}

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int a[110];
int sum[110];
int dp[110][110];
const int INF = (1 << 30);
int solve(int l, int r)
{
	if (dp[l][r] != -1)
		return dp[l][r];
	int res = INF;
	for (int i = l; i <= r - 1; i++)
		res = min(res, solve(l, i) + solve(i + 1, r) + sum[r] - sum[l - 1]);
	return dp[l][r] = res;
}
int main()
{
	int n;
	scanf("%d", &n);
	for (int i = 1; i <= n; i++)
	{
		scanf("%d", &a[i]);
		sum[i] = sum[i - 1] + a[i];
	}
	memset(dp, -1, sizeof(dp));
	for (int i = 1; i <= n; i++)    //注意要初始化为0
		dp[i][i] = 0;
	printf("%d\n", solve(1, n));
	return 0;
}