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package g0301_0400.s0307_range_sum_query_mutable;
// #Medium #Array #Design #Segment_Tree #Binary_Indexed_Tree
// #2022_07_07_Time_99_ms_(88.96%)_Space_138.9_MB_(5.17%)
public class NumArray {
private int[] nums;
private int sum;
public NumArray(int[] nums) {
this.nums = nums;
sum = 0;
for (int num : nums) {
sum += num;
}
}
public void update(int index, int val) {
sum -= nums[index] - val;
nums[index] = val;
}
public int sumRange(int left, int right) {
int sumRange = 0;
if ((right - left) < nums.length / 2) {
// Array to sum is less than half
for (int i = left; i <= right; i++) {
sumRange += nums[i];
}
} else {
// Array to sum is more than half
// Better to take total sum and substract the numbers not in range
sumRange = sum;
for (int i = 0; i < left; i++) {
sumRange -= nums[i];
}
for (int i = right + 1; i < nums.length; i++) {
sumRange -= nums[i];
}
}
return sumRange;
}
}