**Interval Painting - Google Top Interview Questions**

### Problem Statement :

You are given a list of integers walks and an integer target. You are currently at position 0 in a one-dimensional line. Each integer abs(walks[i]) represents the number of steps taken. Positive value means you walked right while negative value means you walked left. We define a "block" as an interval of length 1 that has been walked on. For example, if you walk right 2 times, then you walked on blocks [0, 1] and [1, 2] once each. If you walk left once, then you'd walk on block [1, 2] again. Return the number of blocks that's been walked on at least target number of times. Constraints 0 ≤ n ≤ 100,000 where n is the length of walks 1 ≤ target Example 1 Input walks = [2, -4, 1] target = 2 Output 3 Explanation graph We move right 2 steps right and then 4 steps left and then 1 step right. So we step on blocks [-2, -1], [0, 1] and [1, 2] 2 times.

### Solution :

` ````
Solution in C++ :
int solve(vector<int> &nums, int target) {
map<int, int> m;
int current = 0;
for (auto n : nums) {
int last = current + n;
if (n >= 0) {
m[current] += 1;
m[last] -= 1;
} else {
m[last] += 1;
m[current] -= 1;
}
current = last;
}
int prev = 0;
for (auto &[x, y] : m) {
y += prev;
prev = y;
}
int s = -1e9, ans = 0;
for (auto &[x, y] : m) {
if (y >= target) {
if (s == -1e9) s = x;
} else {
if (s != -1e9) {
ans += (x - s);
s = -1e9;
}
}
}
return ans;
}
```

` ````
Solution in Java :
import java.util.*;
class Solution {
public int solve(int[] nums, int target) {
Map<Integer, Integer> map = new TreeMap<>();
int curr = 0;
for (int num : nums) {
int left = curr, right = curr;
if (num < 0)
left += num;
else
right += num;
map.put(left, map.getOrDefault(left, 0) + 1);
map.put(right, map.getOrDefault(right, 0) - 1);
curr += num;
}
int res = 0, prev = 0, walk = 0;
for (int key : map.keySet()) {
if (walk >= target)
res += Math.abs(key - prev);
walk += map.get(key);
prev = key;
}
return res;
}
}
```

` ````
Solution in Python :
class Solution:
def solve(self, nums, target):
pos = 0
jumps = defaultdict(int)
for dist in nums:
jumps[pos] += 1 if dist > 0 else -1
jumps[pos + dist] -= 1 if dist > 0 else -1
pos += dist
lastpos = level = total = 0
for pos, val in sorted(jumps.items()):
if level >= target:
total += pos - lastpos
level += val
lastpos = pos
return total
```

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