AtCoder Beginner Contest 183(A-E)

A - ReLU

def main():
      x = int(input())
      print(x if x >= 0 else 0)

if __name__ = "__main__":
      main()

B - Billiards

def main():
      a,b,c,d = map(int,input().split())
      print((b*c+a*d)/(b+d))

C - Travel

(O(n!))暴力

#include <bits/stdc++.h>

using namespace std;
const int NMAX = 2e5 + 10;
typedef long long ll;

int T[100][100];
int main()
{
	int n , k;
	int a[10];
	scanf("%d%d",&n,&k);
	for(register int i = 1;i <= n;i++)
		for(register int j = 1;j <= n;j++)
			scanf("%d",&T[i][j]);
	for(register int i = 2,j = 1;i <= n;i++)
	{
		a[j] = i;
		j++;
	}
	
	int ans = 0;
	do{
		int tot = 0;
		tot += T[1][a[1]];
		for(register int i = 2;i < n;i++)
			tot += T[a[i]][a[i-1]];
		tot += T[a[n-1]][1];
		if(tot == k)	ans++;
	}while(next_permutation(a+1,a+n));
	printf("%d
",ans);
	return 0;	
}

D - Water Heater

前缀和

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int NMAX = 2e5 + 10;
ll liter[NMAX];
int main()
{
	int n, max_time = 0;ll L;
	scanf("%d%lld",&n,&L);
	for(register int i = 1;i <= n;i++)
	{
		int l, r;
		ll lit;
		scanf("%d%d%lld",&l,&r,&lit);
		liter[l + 1] += lit;
		liter[r + 1] -= lit;
		max_time = max(max_time , r + 1);
	}
	bool flag = true;
	for(register int i = 1;flag &&i <= max_time;i++)
	{
		liter[i] += liter[i - 1];
		if(liter[i] > L)
		{
//			printf("%d
",liter[i]);
			flag = false;
		}
	}
	printf("%s
",flag?"Yes":"No");
	return 0;
}

E - Queen on Grid

动态规划，维护行、列、对角线的前缀和

#include <bits/stdc++.h>

using namespace std;
const int NMAX = 2e3 + 10;
const int MOD = 1e9 +7;
typedef long long ll;

char str[NMAX][NMAX];
ll col_sum[NMAX][NMAX], row_sum[NMAX][NMAX],diag_sum[2*NMAX][NMAX];  // lie hang duijiaoxian
int col_max[NMAX], row_max[NMAX], diag_max[2*NMAX];


ll colSum(int index,int l,int r)
{
	return (col_sum[index][r] - col_sum[index][l] + MOD)%MOD;
}

ll rowSum(int index,int l,int r)
{
	return (row_sum[index][r] - row_sum[index][l] + MOD)%MOD;
}

ll diagSum(int index,int l,int r)
{
	return (diag_sum[index][r] - diag_sum[index][l] + MOD)%MOD;
}
int main()
{
	int h, w;
	scanf("%d%d",&h,&w);
	for(register int i = 1;i <= h;i++)
		scanf("%s",str[i] + 1);	
	ll ans = 0;
	for(register int i = 1;i <= h;i++)
		for(register int j = 1;j <= w;j++)
		{
			if(i == j && i == 1)
			{
				row_sum[1][1] = col_sum[1][1] = diag_sum[w][1] = 1;
				continue;
			}
			if(str[i][j] == '#')
			{
				ans = 0;col_max[j] = i;row_max[i] = j;diag_max[i - j + w] = min(i,j);
			}
			else
			{
				ans = (colSum(j,col_max[j],i - 1) + rowSum(i,row_max[i],j - 1) + diagSum(i - j + w,diag_max[(i - j + w)],min(i,j)-1))%MOD;
			}
			row_sum[i][j] = (row_sum[i][j-1] + ans)%MOD;
			col_sum[j][i] = (col_sum[j][i-1] + ans)%MOD;
			diag_sum[i - j + w][min(i,j)] = (diag_sum[i - j + w][min(i,j)-1] + ans)%MOD;
//			printf("%lld%c",ans,j == w?'
':' ');
		}
	printf("%lld
",ans);
	return 0;	
}