UVa12532 - Interval Product(Fenwick树)

#include <cstdio>
#include <vector>

using namespace std;

const int N = 100010;

struct Fenwick
{
private:
	vector<int> fw;
	
public:
	int lowbit(int n)
	{
		return n & (-n);
	}
	
	void init(int n)
	{
		fw.assign(n + 1, 0);
	}
	
	int sum(int n)
	{
		int s = 0;
		while (n > 0) {
			s += fw[n];
			n -= lowbit(n);
		}
		
		return s;
	}
	
	int sum(int a, int b)
	{
		return sum(b) - (a == 1 ? 0 : sum(a - 1));
	}
	
	void adjust(int k, int v)
	{
		while (k < (int)fw.size()) {
			fw[k] += v;
			k += lowbit(k);
		}
	}
};

struct solution
{
private:
	int x[N];
	int n, k;
	Fenwick neg, zero;
	
public:
	bool input()
	{
		if (scanf("%d%d", &n, &k) != 2) return false;
		
		neg.init(n);
		zero.init(n);
		
		for (int i = 1; i <= n; i++) {
			scanf("%d", &x[i]);
			if (x[i] < 0) neg.adjust(i, 1);
			else if (x[i] == 0) zero.adjust(i, 1);
		}
		
		return true;
	}
	
	void solve()
	{
		for (int i = 0; i < k; i++) {
			char ch;
			scanf("%c", &ch);

			while (ch != 'P' && ch != 'C') {
				scanf("%c",  &ch);
			}
			
			int a, b;
			scanf("%d%d", &a, &b);
			
			if (ch == 'P') {
				if (zero.sum(a, b)) {
					printf("0");
				} else if (neg.sum(a, b) & 1) {
					printf("-");
				} else {
					printf("+");
				}
			} else {
				if (x[a] < 0 && b >= 0) {
					neg.adjust(a, 1);
				} else if (x[a] >= 0 && b < 0) {
					neg.adjust(a, 1);
				}
				
				if (x[a] != 0 && b == 0) {
					zero.adjust(a, 1);
				} else if (x[a] == 0 && b != 0) {
					zero.adjust(a, -1);
				}
				
				x[a] = b;
			}
		}
		
		printf("\n");
	}
};

int main()
{
#ifndef ONLINE_JUDGE
	freopen("d:\\OJ\\uva_in.txt", "r", stdin);
#endif

	solution solver;
	while (solver.input()) {
		solver.solve();
	}
	 
	return 0;
}