UVa 12532 - Interval Product

題目：已知N各數字X1~Xn，執行兩種操作：1、改變Xi為A；2、求區間[L，R]上元素乘積的符號。

分析：DS，線段樹。利用線段樹處理即可，每個數字正的取1，負的取-1，否則取0。

說明：╮(╯▽╰)╭。

#include <cstdlib>
#include <cstring>
#include <cstdio>

int data[100001];

//segment_tree__begin
typedef struct tnode
{
	tnode* Lchild;
	tnode* Rchild;
	int    Lvalue;
	int    Rvalue;
	int    Value;
}tnode;

tnode  Node[200002];
tnode* Root;
int    Count;

tnode* buildtree(int a, int b) 
{
	tnode* np = &Node[Count ++];
	np->Lvalue = a;
	np->Rvalue = b;
	np->Value = 0;
	if (a < b) {
		np->Lchild = buildtree(a, (a+b)/2);
		np->Rchild = buildtree((a+b)/2+1, b);
	}else {
		np->Lchild = NULL;
		np->Rchild = NULL;
	}
	return np;
} 

void segment_tree(int a, int b)
{
	Count = 0;
	Root = buildtree(a, b);
}

void Insert(tnode*r, int a, int b, int v) 
{
	if (r->Lvalue == a && r->Rvalue == b) {
		r->Value = v;
		return;
	}
	if (b <= r->Lchild->Rvalue) {
		Insert(r->Lchild, a, b, v);
	}else if (a >= r->Rchild->Lvalue) {
		Insert(r->Rchild, a, b, v);
	}
	r->Value = r->Lchild->Value * r->Rchild->Value;
}

int Query(tnode* r, int a, int b) 
{
	if (r->Lvalue == a && r->Rvalue == b) {
		return r->Value;
	}else if (b <= r->Lchild->Rvalue) {
		return Query(r->Lchild, a, b);
	}else if (a >= r->Rchild->Lvalue) {
		return Query(r->Rchild, a, b);
	}else {
		return Query(r->Lchild, a, r->Lchild->Rvalue) * Query(r->Rchild, r->Rchild->Lvalue, b);
	}
}

void Insert(int a, int b, int v) 
{
	Insert(Root, a, b ,v);
}

int Query(int a, int b) 
{
	return Query(Root, a, b);
}
//segment_tree__end 

int main()
{
	int  N, K, value1, value2, ans;
	char operators[2];
	while (~scanf("%d%d",&N,&K)) {
		for (int i = 1; i <= N; ++ i) {
			scanf("%d",&data[i]);
		}
		segment_tree(1, N);
		for (int i = 1; i <= N; ++ i) {
			if (data[i] > 0) {
				Insert(i, i, 1);
			}else if (data[i] < 0) {
				Insert(i, i, -1);
			}else {
				Insert(i, i, 0);
			}
		}
		for (int i = 1; i <= K; ++ i) {
			scanf("%s%d%d",operators,&value1,&value2);
			if (operators[0] == 'C') {
				if (value2 > 0) {
					Insert(value1, value1, 1);
				}else if (value2 < 0) {
					Insert(value1, value1, -1);
				}else {
					Insert(value1, value1, 0);
				}
			}else {
				ans = Query(value1, value2);
				if (ans > 0) {
					printf("+");
				}else if (ans < 0) {
					printf("-");
				}else {
					printf("0");
				}
			}
		}
		puts("");
	}
	return 0;
}