NYOJ 108 士兵杀敌（一）

#include <iostream>
#include <stdio.h>
using namespace std;
const int maxn = 1000005;
int ans[maxn], n;
int lowbit(int x)
{
return x & (-x);
}

int getSum(int x)
{
int i, sum=0;
for(i = x; i > 0; i-=lowbit(i))
sum += ans[i];
return sum;
}

int mod(int x, int num)
{
int i;
for(i = x; i <= n; i+=lowbit(i))
ans[i] += num;
}

int main()
{
int m, i, j, a, b;
scanf("%d%d",&n,&m);
for(i=1;i<=n;i++)
{
scanf("%d",&a);
mod(i,a);
}
while(m--)
{
scanf("%d%d",&a,&b);
printf("%d\n",getSum(b)-getSum(a-1));
}
return 0;
}