TYVJ 1512 异或密码 解题报告

　　可以用朴素算法，在TYVJ上2000ms，别的评测机可能超时，所以修改成了线段树的，代码如下：

#include <stdio.h>
#include <stdlib.h>
struct tree{
	int l, r;
	int ll, rr;
	int xor;
}tree[100001];
int end;
int num[50000];

int maketree(int s, int t)
{
	int l = end++;
	tree[l].l = s;
	tree[l].r = t;
	if(s == t){
		tree[l].ll = tree[l].rr = -1;
		tree[l].xor = num[s];
		return num[s];
	}
	tree[l].ll = end;
	tree[l].xor = maketree(s, (s + t) / 2);
	tree[l].rr = end;
	tree[l].xor ^= maketree((s + t) / 2 + 1, t);
	return tree[l].xor;
}

int deal(int r, int s, int t)
{
	int mid;
	if(tree[r].l == s && tree[r].r == t){
		return tree[r].xor;
	}
	mid = (tree[r].l + tree[r].r) / 2;
	if(t <= mid){
		return deal(tree[r].ll, s, t);
	}else if(s > mid){
		return deal(tree[r].rr, s, t);
	}
	return deal(tree[r].ll, s, mid) ^ deal(tree[r].rr, mid + 1, t);
}

void fix(int r, int a, int b)
{
	int mid = (tree[r].l + tree[r].r) / 2;
	if(tree[r].l == a && tree[r].r == a){
		tree[r].xor = b;
		return;
	}
	if(a <= mid){
		fix(tree[r].ll, a, b);
	}else{
		fix(tree[r].rr, a, b);
	}
	tree[r].xor = tree[tree[r].ll].xor ^ tree[tree[r].rr].xor;
}

int main(int argc, char **argv)
{
	int i;
	int n, m;
	int a, b, c;
	scanf("%d%d", &n, &m);
	for(i = 0; i < n; i++){
		scanf("%d", &num[i]);
	}
	maketree(0, n - 1);
	for(i = 0; i < m; i++){
		scanf("%d%d%d", &a, &b, &c);
		if(a){
			fix(0, b - 1, c);
		}else{
			printf("%d\n", deal(0, b - 1, c - 1));
		}
	}
	return 0;
}