Submission #1869901

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Source Code Expand

#include <cstdio>

#define iter(i, n) forw(i, 1, n)
#define iter0(i, n) for (int i = 0; i < n; ++i)
#define forw(i, a, b) for (int i = a; i <= b; ++i)

const int NR = 3010;
const int mod = 1e9 + 7;

int n, m;
int f[NR][NR][2];

inline void inc(int &x, int y) { x = (x + y) % mod; }

int main() {
	scanf("%d%d", &n, &m);

	//a[1] a[2] a[3]

	if (n == 1) {
		int ans = 2;
		iter(i, m) ans = ans * 2 % mod;
		printf("%d\n", ans);
		return 0;
	}

	forw(i, 0, n) f[0][i][i == 0] = 1;
	
	iter0(i, m) {
		forw(j, 0, n) iter0(k, 2) if (f[i][j][k]) {
			int w = f[i][j][k];
			if (j) {
				inc(f[i + 1][j][k | (j == 1)], w);
				inc(f[i + 1][j - 1][k | (j == 1)], w);
			}
			if (j < n) {
				inc(f[i + 1][j][k], w);
				inc(f[i + 1][j + 1][k], w);
			}
		}
	}
	int ans = 0;
	forw(j, 0, n) inc(ans, f[m][j][1]);
	printf("%d\n", ans);
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:16:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
                       ^

Judge Result